Chemistry World _ Scientists

Aristotle was one of the greatest thinkers of the ancient world. Aristotle was deeply interested in the philosophy of nature, devoting much thought the relation ship between form and matter and the nature of change. Another important area for thought about Aristotle was the nature of knowledge itself. Aristotle ideas strongly influenced the development of thought in western civilization, especially through the middle ages in the Christian nations of Europe and the Islamic world.

In addition to his philosophic contemplations, Aristotle collected a large number of observations about the physical world, particularly of living things. In fact, Aristotle may be considered the first great biologist He examined the structure of plants and animals and observed the behavior of animals. He also classified living things in groups according to their common traits rather than their usefulness to humans.

One measure of Aristotle's influence on the modern world is the large number of words in modern languages that can be traced back to his teaching and writings. For example, the terms of grammar, subject and predicate, come from Aristotle. Also, many words used to describe basic scientific principles are Aristotle's. These include matter, energy, potential, cause, genus, species, and many others. Mathematics relies on such vocabulary as quantity, relation-also words of Aristotle. Many of these words have come into modern languages through Latin, rather than directly from Greek. Aristotle was born the son of a physician who attended the king of Macedonia. At the age of about 18, he entered the great philosopher Plato's school in Athens, the Academy. Aristotle remained at the Academy for about 20 years, then joined a group of Plato's disciples for some 3 years afterward. In about 343 B.C., Aristotle went to the court of King Philip II of Macedonia to supervise the education of Alexander, the king's son. Aristotle thus had the opportunity to influence the future world conqueror, Alexander the Great. After Alexander reached maturity, Aristotle returned to Athens and founded the Lyceum, his own school. The method and philosophy associated with the Lyceum came to be known as peripatetic-a Greek word for walking about-because Aristotle taught while walking with his students. In 323 Aristotle fled the Athenians, who had trumped up a charge against him, and settled in the city of Chalcis, where he spent his final year. Relatively few of Aristotle's written works survive. We know of the existence of many more because of references in the works of other writers of ancient times.

Bacon,Roger (1214?-1292?) was an English philosopher and scientist, a major early sup-porter of experimental science. Bacon was known widely and popularly in his day and gained the title doctor mirabilis, which is Latin for "wonderful teacher." Bacon conducted studies in many fields, including mathematics, astronomy, optics, and alchemy, an early form of chemistry. Though he described spectacles and gave exact directions for making gunpowder, Bacon is most remembered today for his insistence on using the experimental method to confirm scientific theories. His scientific skepticism and commitment to method and experimentation were well known in his own day.

Bacon's own most significant researches, those in the field of optics, reveal careful experimentation and interpretation of results. Roger Bacon was born into a wealthy English family and enjoyed the educational advantages his social rank afforded. He was educated at Oxford University and later at the University of Fans, where he also taught. Around 1247, Bacon returned to Oxford, where he seems to have undergone a considerable change in his thinking, possibly due to the influence of the great scholar Robert Grosseteste. Thus began for Bacon an intensive, decade-long period of scientific research. The year 1257 marked another great change in Bacon's life, for the scientist-scholar joined the Franciscan religious order. From this time until his death in or around 1292, Bacon's career was enmeshed in politics of the pope and the Franciscan order. He was even imprisoned for a time by the Franciscans for controversial writings. Nevertheless, Bacon managed to produce a large volume of writings in the period from 1257 until his death. In his greatest treatise, the Opus Maius(Longer Work), Bacon urged the pope to undertake a program of educational reform in which new areas of scientific study would be opened in universities of the West. The death of the somewhat sympathetic Pope Clement IV in 1268 ended Bacon's hopes for these plans.

Boyle,Robert (1627-1691), an Anglo-Irish scientist, was a founder of modern chemistry and founding member of the Royal Society of London. Boyle conducted fundamental experiments on gases. He also attacked anciently held scientific theories, including Aristotle's notion that the universe is made up of the four elements: earth, air, fire, and water. Instead, Boyle proposed that all matter is composed of primary particles (which he called "corpuscles") that combine in different ways and pro-portions to produce different substances. Boyle's "corpuscular" theory laid the groundwork for development of a modern atomic theory in the nineteenth century.

Boyle demonstrated through experiments that air is necessary for fire, breathing, and sound. Experimentation led him to conclude a basic property of gases, which came to be known as Boyle's law: the volume of a gas at a constant temperature varies inversely to the pressure applied to the gas. Boyle also proposed a method to distinguish acids from alkalines. Although born in Ireland, Boyle was a Protestant and lived mostly in England as an adult. He displayed considerable interest in religion, especially in later life, and wrote a theological work, The Chrisfldn ½rtuoso, in 1690. Boyle also published numerous works on his experiments, including a treatise on gases in 1660 and a work presenting his theory of matter in 1661.

Newton, Sir Isaac (1642-1727), mathematician and physicist, one of the foremost scientific intellects of all time. Born at Woolsthorpe, near Grantham in Lincolnshire, where he attended school, he entered Cambridge University in 1661; he was elected a Fellow of Trinity College in 1667, and Lucasian Professor of Mathematics in 1669. He remained at the university, lecturing in most years, until 1696. Of these Cambridge years, in which Newton was at the height of his creative power, he singled out 1665-1666 (spent largely in Lincolnshire because of plague in Cambridge) as “the prime of my age for invention”. During two to three years of intense mental effort he prepared Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy) commonly known as the Principia, although this was not published until 1687.

As a firm opponent of the attempt by King James II to make the universities into Catholic institutions, Newton was elected Member of Parliament for the University of Cambridge to the Convention Parliament of 1689, and sat again in 1701-1702. Meanwhile, in 1696 he had moved to London as Warden of the Royal Mint. He became Master of the Mint in 1699, an office he retained to his death. He was elected a Fellow of the Royal Society of London in 1671, and in 1703 he became President, being annually re-elected for the rest of his life. His major work, Opticks, appeared the next year; he was knighted in Cambridge in 1705.

As Newtonian science became increasingly accepted on the Continent, and especially after a general peace was restored in 1714, following the War of the Spanish Succession, Newton became the most highly esteemed natural philosopher in Europe. His last decades were passed in revising his major works, polishing his studies of ancient history, and defending himself against critics, as well as carrying out his official duties. Newton was modest, diffident, and a man of simple tastes. He was angered by criticism or opposition, and harboured resentment; he was harsh towards enemies but generous to friends. In government, and at the Royal Society, he proved an able administrator. He never married and lived modestly, but was buried with great pomp in Westminster Abbey.

Newton has been regarded for almost 300 years as the founding examplar of modern physical science, his achievements in experimental investigation being as innovative as those in mathematical research. With equal, if not greater, energy and originality he also plunged into chemistry, the early history of Western civilization, and theology; among his special studies was an investigation of the form and dimensions, as described in the Bible, of Solomon's Temple in Jerusalem.

Bernoulli, Daniel (1700-1782), Dutch-born Swiss scientist, who discovered the basic principles of fluid behaviour. He was the son of Johann Bernoulli and the nephew of Jakob Bernoulli, both of whom made major contributions to the early development of calculus.

Bernoulli was born in Groningen, the Netherlands, on January 29, 1700, and took an early interest in mathematics. Although he earned a medical degree in 1721, he became a Professor of Mathematics at the Russian Academy in St Petersburg in 1725. He later taught experimental philosophy, anatomy, and botany at the universities of Groningen and Basle, Switzerland.

Bernoulli pioneered in Europe the acceptance of the new physics of the English scientist Isaac Newton. He studied the flow of fluids and formulated the principle that the pressure exerted by a fluid is inversely proportional to its rate of flow. He used atomistic concepts in trying to develop the first kinetic theory of gases, accounting for their behaviour under conditions of changing pressure and temperature in probabilistic terms. This work, however, did not gain wide notice at the time. Bernoulli died in Basle on March 17, 1782.

Cavendish,Henery (1731-1810) was an English physicist and chemist who made fundamental discoveries in a number of scientific fields, although several of them remained unpublished in his lifetime. Cavendish was exceptionally brilliant but highly eccentric as well. In fact, Cavendish probably fit some of the "mad scientist" stereotypes. He almost totally avoided contact with other people, spoke very little, and went about in shabby clothing. But Cavendish possessed one of the most brilliant minds and conducted some of the most original experiments of his age. Cavendish did important experimental work in chemistry. He studied air and gases extensively. Cavendish was among the first scientists to recognize that hydrogen is a separate element. Experiments he conducted in 1784-1 785 led Cavendish to the conclusion that water is a compound of hydrogen and air (oxygen). The chemist Joseph Priestley had done the same experiments but had missed the importance of the water vapor produced when hydrogen and oxygen ignite. Cavendish also performed some experiments with carbon dioxide.

Cavendish made fundamental discoveries in electricity. He anticipated the work of several later scientists, but most of his work on electricity went unpublished for years. Almost a century later, the English physicist James Clerk Maxwell recovered Cavendish's findings, publishing some of them in 1879. Cavendish discovered the law of electricity that later became known as Coulomb's law (and Coulomb's discovery). This law states that the force of two electrical charges is inverse to the square of the distance between them. Cavendish anticipated Ohm's Law as well by observing that the electrical potential across two conductors is directly proportional to the current between them. Cavendish also discovered that all points on the surface of a good conductor are at the same potential with respect to the earth. This idea proved very important later in the development of electrical theory. Cavendish had no instrument for measuring electrical current. He used his own body as a meter, grasping an electrode with each hand and then judging how far from his fingertips the shock spread.

Henry Cavendish was born in Nice, France, a descendant of the Duke of Devonshire and the Duke of Kent. He attended Cambridge University but did not obtain a degree. For many years Cavendish lived with his father, also a distinguished scientist, in London. The two Cavendishes performed many experiments together. Henry's father died in 1783. Henry Cavendish was elected to the Royal Academy in 1760. He became a foreign associate of the Institute of France in 1803. Cavendish possessed an enormous fortune, which he left to family members at his death in 1810. Many years later, in 1871, the Cavendish family endowed the Cavendish Laboratory at Cambridge, where many of the modern discoveries in physics have been made.

Priestley,Joseph (1733-1804) was one of 1) most original thinkers of the English-speakers world in the 1700's.
Priestley made fundamental contributions to science. He discovered ygen and about 10 other gases. He discover basic principles of photosynthesis and con ducted early experiments in electricity. Priestley was a freethinker in religion and a sup-porter of popular government, that is, government by the people.
Priestley's most famous achievement is his discovery of oxygen in 1774. (Actually, a Swedish chemist, Carl Scheele, discovered oxygen at about the same time as Priestley. Today, both scientists are given the credit.) Priestle called the substance "de-phlogisticated air" took this name from a theory that was then current, but later proved false-the phlogiston theory. This theory stated that all flammable materials (those that will burn) contain a substance called phlogiston. (The phl letter group in phlogiston is pronounced like fl) When a substance burns, it gives up its phlogiston to the air. Friestley knew that substances burn the presence of oxygen. He therefore assumed that oxygen readily absorbs the phlogiston given oft by the burning substances. According to his thinking, the oxygen originally contained no phlogiston. It was "dephlogisticated" At about the same time, the great French chemist Antoine Lavoisier was conducting similar experiments.

Priestley met Lavoisier France in 1775. He gave Lavoisier detailed accounts of his experiments with the "dephlogisticated" air. Lavoisier repeated Priestley's experiments. He recognized the true nature of the gas-that it was a basic chemical element-and gave it the name oxygen. He also discovered that oxygen combines chemically with other substances during combustion.
Priestley was a great experimenter who had talent for designing new laboratory devices when experiments required them. He was able to isolate, identify, and study a number of gases. These included nitrogen, nitrous oxide, nitrogen dioxide, nitrous oxide (laughing gas), hydrogen chloride, ammonia, sulfur dioxide silicon tetrafluoride, and carbon monoxide ( gas we know today as part of car exhaust fumes).
Priestley studied carbonation in liquids. He went to a beer factory and observed the bubbles of carbon dioxide that develop in a fermenting liquid. Later Priestley developed a method for carbonating water. His work made possible the soda-water industry. (We use carbonated water today in products such as soft drinks and soda water.)
Priestley made some of the first important discoveries on plant photosynthesis. In photosynthesis, green plants use the sun's energy to change water and carbon dioxide into sugar, a basic food. Priestley discovered that green plants give off oxygen. He also noted that green plants need sunlight Scientists studying photosynthesis in the late 1 700's used these observations in their research.

Near the beginning of his scientific career, Priestley conducted experiments in electricity. He observed a relationship between electricity and chemical changes. Later, Priestley used an electric spark to decompose (break down) ammonia. This process is called e/ectrolysis. Although Priestley is not credited with discovering electrolysis, his work paved the way for later discoveries. With the help of his friend, Benjamin Franklin, Priestley published in 1767 an important book on electricity. Entitled The History and Present state of Electricity this book summed up the knowledge about electricity at that time and reported some of Priestley's own experiments. Very successful and popular, the book went into five editions. Priestley also conducted experiments in optics, the study of light and vision. In 1772 he published his experimental findings and theories in a book called History and Present state of Discoveries Relating to Vision, Light and Colours.
Joseph Priestley was born in Yorkshire (northeastern England) in 1733. His parents were dissenters, people who did not belong to the Church of England. Although England allowed some religious freedom at this time, dissenters were barred from many professions, schools, and universities.

Young Joseph Priestley entered Northampton Academy, a school run by dissenters, in 1752. There he received an excellent education. He trained to be a teacher and a minister. Priestley was appointed a teacher at a dissenting academy in Warrington. While there he put many new ideas of education into practice. The dissenting schools had great freedom to develop curriculum (the course of study in a school) because the state church and the government were not involved. Priestley developed a new approach to leaching English grammar. He based his method on current English usage rather than models provided by the ancient classical languages (such as Greek and Latin). He also molded the school's curriculum to prepare students for careers in science, industry, the arts, and commerce. Under Priestley's influence, his academy became per haps the best dissenting school in England. In a recognition of his educational work, Priestley received an honorary doctoral degree from the University of Edinburgh, Scotland, in 1765. During the 1760's, Priestley became friends with Benjamin Franklin, who was then serving in London. At about this time Priestley began serious scientific experimentation. In 1766 Priestley was elected to the Royal Society of London. Priestley's scientific career received a boost In 1772 when the Earl of Shelburn, a wealthy nobleman, became his patron In return for tutoring the earl's children, Priestley received a salary and plenty of free time in which to experiment. In 1779 Priestley left Shelburn's household to become minister to a dissenting congregation in Birmingham, England. During this penod, Priestley wrote many theological works. He became more and more radical, rejecting many traditional Christian doctrines. He earned a controversial reputation as a freethinker for his religious and political opinions. When the French Revolution broke out in 1789, Priestley vocally supported it. Many locale people became angry with Priestley because of his radical ideas. On July 14, 1791, a mobbroke into Priestley's house, destroying everything, including his library and laboratory. Priestley and his family escaped Birmingham. Eventually, they immigrated to the United States. In 1794 Priestley and his wife settled in Northumberland, Pennsylvania. Their Priestley continued to write religious and political works. He became friends with John Adams and Thomas Jefferson. Both of these men admired Priestley's free spirit and intellect and agreed with many of his ideas. Joseph Priestley died in 1804.

Lavoisier,Antoine (1743-1794) was a great French chemist who is often called the father of modern chemistry. Lavoisier was a scientist and thinker of unusually wide interests. He made contributions to many scientific fields. Lavoisier's brilliant scientific career was cut short by radicals of the French Revolution who had him executed by the guillotine in 1794. Lavoisiers most important contribution to science was his explanation of the chemical basis of combustion (fire). He observed that when the chemical elements sulfur and phosphorus are burned, they increase in weight.

Lavoisier correctly assumed that these elements had combined chemically with air during combustion. Lavoisier did not know at that time, however, exactly what elements make up air. Then in 1774, Joseph Priestley of England discovered oxygen. (Priestley used a different name for the element; it is Lavoisier who coined the name "oxygen" Lavoisier realized that this element-oxygen-combines with substances when they burn.
Lavoisier's theories led to the rejection of the phlogistic doctrine, which had been accepted as a basic principle of chemistry for many years. This doctrine claimed that all flammable materials (materials that will burn) contain a substance called phlogiston. (The phl letter-group in phlogiston is pronounced like fl) When a substance burns, it gives up its phlogiston to the air, according to the theory. When Priestley discovered oxygen, for instance, he believed he had discovered dephlogisticated air He knew that substances burn in the presence of oxygen. He therefore assumed that oxygen readily absorbs the phlogiston given oft by the burning substances. This must mean that oxygen normally contains no phlogiston; therefore, it is "dephlogisticated."
Lavoisier, however, understood that oxygen combines with substances during combustion. By weighing the matter before and after combustion, he was able to confirm this idea. Lavoisier's discovery was one of the most important in the history of chemistry. It led to another important discovery-that matter cannot be created or destroyed, only changed in form. This important principle is known as the law of conservation of matter. Lavoisier developed a method for describing mathematically the chemical changes that matter can undergo. This method is the chemical equation. In a chemical equation, the mass of matter on the left side of the equation (before a chemical change) must equal the mass on the right side (after a chemical change). All chemists since Lavoisier's time have used the chemical equation in their work. Lavoisier also helped develop the system of chemical names now used.

Lavoisier also made the fundamental discovery that water is made of hydrogen and oxygen. Unknown to him, the English chemist Henry Cavendish had discovered this fact a short time earlier. Lavoisier studied respiration in animals as a chemical process. He came to the conclusion that respiration is a kind of combustion. In respiration, oxygen is chemically combined wit) nutrients such as simple sugars. In this chemical reaction, heat is given off. Heat is a form of energy an organism must use to stay alive. Also, waste products such as carbon dioxide are given off. In describing respiration chemically, Lavoisier laid the foundation for modern biochemistry Lavoisier published his doctrines of chemistry in the Elementary Treatise on Chemistry in 1789. This became one of the most important early textbooks on chemistry. It also enabled other chemists to learn about Lavoisie ideas. Lavoisier was involved in public service for much of his adult life. This career gave Lavoisier many opportunities to apply his mathematical and scientific talents to practical use. As a young man, he joined the geologist J. Guettard in a geological survey trip through out France. Afterward, Lavoisier helped Guettard prepare a mineralogical atlas of France. He helped improve the manufacture of gunpowder. In agriculture, he established a model farm where principles of scientific agriculture were demonstrated. Also, Lavoisier served on the commission that devised the metric system, a uniform and scientific system of measurements. The French government adopted the metric system in 1795. Today it is used in most countries of the world and is the system of measurement used in science.

Antoine Lavoisier was born in 1743 of a well- to-do family in Paris. He received an excellent education. In 1766 young Lavoisier won gold medal from the French Academy of Sciences for a plan of lighting city streets. Two years later he became a member of the Academy. Lavoisier received a title of nobility in 1772. He also served in the French civil service, notably as a member of the nation's tax-collecting body. For these reasons, Lavoisier became the target of radical politicians who seized power in the early 1790's during the French Revolution. In 1792 Lavoisier was forced to leave hi.' house and laboratory. In May, 1 794, he was ~ rested and forced to stand trial. The revolutionaries made no effort to give Lavoisier a trial. He was convicted and condemned to death. Lavoisier was beheaded by the guillotine on May 8,1794.

Dalton,John (1766-1844) was a highly original English scientist who studied a wide range of topics in science. Dalton is best known, however, for his contributions to the atomic theory in of matter. The atomic theory proposes that all matter is made up of very tiny particles called atoms. Dalton refined the theory by suggesting that each chemical element consists of a Single type of atom. Although an amount of the element may contain many, many atoms, they are all identical in size, shape, and mass. Further-more, Dalton theorized that in a chemical compound, the atoms of the different elements always combine in the same ratio.
In a similar vein, Dalton arranged all of the known chemical elements in a table according to atomic weight (Dalton understood that each element has a unique atomic weight, since the atoms of each element are unique.) Dalton's table was a very early version of the periodic table developed in the later 1800's by Dmitri Mendeleev and others. Dalton also devised a system of chemical symbols to use in formulas.

Dalton made fundamental contributions to the scientific understanding of gases. He first stated the law of partial pressures. This law e plains that the total pressure in a mixture of gases equals the sum of the pressure exerted independently by each gas. It is now called Dalton's law. Another chemical law credited to Dalton states that a gas expands as it is heated (This law is now called Charles' law -even though Dalton really discovered it first) And, Dalton proved that gases dissolve in water. H also proved the rate of diffusion of gases. Early in life, Dalton developed a strong interest in meteorology, the scientific study of weather. He was one of the first people to study weather from a scientific viewpoint. Dalton confirmed that rain falls when the temperature of a cloud declines, not because of a drop in atmospheric pressure. He also developed a theory to explain the cause of the trade winds, which occur in the latitudes of the earth near the equator. Dalton said that the trade winds were caused by a combination 0 the earth's rotation and temperature variation in the earth's atmosphere. Dalton studied the aurora borealis an occasional brilliant, shimmering display of lights in the northern skies He concluded that the earth's magnetism was at least part of the cause of the aurora. Later scientific findings proved Dalton largely correct in these theories. Dalton also investigated the condition known as color blindness. John and his brother had this condition, in which a person fails to perceive colors accurately. Because ol Dalton's work, the condition of color blindness. is also known as Daltonism. A member of the Royal Society, DaIton received a Gold Medal in 1826. He was also a corresponding member of the French Academy of Sciences and a founding member of the British Association for the Advancement Science. John Dalton died in 1844.

Davy,sir Humphry (1778-1829), an English chemist, isolated several chemical elements, discovered certain chemical compounds, and conducted experiments in electrochemistry. A gifted theoretical and experimental scientist, Davy frequently applied scientific knowledge to practical problems, most notably as the inventor of the miner's safety lamp. An admired lecturer, Davy popularized science in the British Isles as well as in Europe. Davy analyzed the workings of a voltaic cell the main component of an electrical battery. He became convinced that a voltaic cell produces electricity from a chemical reaction, specifically the chemical combination of two substances having opposite charges. From thi.' conclusion, he reasoned that electrolysis could be used to break down chemical compounds into basic chemical elements. Electrolysis is the use of electric current to cause chemical reactions in certain substances. Davy's conclusion proved correct. Using electrolysis, he isolated the elements sodium and potassium from their compounds in 1807. In 1808 he isolated the alkaline-earth metals, a group of chemical elements including calcium, magnesium, barium, and strontium. He also discovered the element boron. Davy was the first scientist to recognize that diamonds are a form of carbon.

Davy studied the common chemical compound, hydrochloric acid. He realized that chlorine is a part of hydrochloric acid but failed to understand that chlorine is a chemical element. He explained in chemical terms how bleach works (by releasing oxygen from water a hydrogen-oxygen compound). In later chemical researches, Davy studied iodine (which he called substance X) and showed its similarity to chlorine. Development of the periodic table of elements some years later would show iodine and chlorine to be closely related, lining up in the table in the same column. Davy examined the relationship between electricity and magnetism. These researches probably influenced his assistant, Michael Faraday, who was destined to become one of the leading scientists in the fields of electricity an~ magnetism. Sir Humphry Davy also discovered a number of practical uses of science. Davy perfected a miner's safety lamp in 1815, an invention that greatly reduced the risks of mine explosions. For this invention and related researches, he won the Rumford gold and silver medals from the Royal Society and a gift of silver from the northern mine owners. In studies of leather tanning processes, Davy found a substance in tropical plants that could be use much more cheaply than oak extracts, which had been used up to that time

Berzelius, Jons Jakob, Baron (1779-1848), Swedish chemist, considered one of the founders of modern chemistry.

Berzelius was born near Linkoping. While studying medicine at the University of Uppsala, he became interested in chemistry. After practising medicine and lecturing, he became a professor of botany and pharmacy at Stockholm in 1807. From 1815 to 1832 he was Professor of Chemistry at the Caroline Medico-Chirurgical Institute in Stockholm. He became a member of the Stockholm Academy of Sciences in 1808, and in 1818 became its permanent secretary. For his contributions to science, Berzelius was made a baron in 1835 by Charles XIV John, King of Sweden and Norway.

Berzelius's research extended into every branch of chemistry and was extraordinary for its scope and accuracy. He discovered three chemical elements—cerium, selenium, and thorium—and was the first to isolate silicon, zirconium, and titanium. He introduced the term catalyst into chemistry and was the first to elaborate on the nature and importance of catalysis. He introduced the present system of chemical notation, in which each element is represented by one or two letters of the alphabet. In addition, Berzelius was primarily responsible for the theory of radicals, which states that a group of atoms, such as the sulphate group, can act as a single unit through a series of chemical reactions. He developed an elaborate electrochemical theory that correctly states that chemical compounds are made up of negatively and positively charged components. All of his theoretical work was supported by elaborate experimental measurement. His greatest achievement was the measurement of atomic weights.

Faraday,Michael (1791-1867), an English chemist and physicist, made very important contributions to scientific knowledge of electricity and magnetism. His work helped make possible the development of electrical power. Moreover, Faraday's theories on electricity and magnetism established the basis for more complete theoretical understanding of these forces.
Faraday also made important discoveries in chemistry. Only a handful of scientists in the 1800's made as great an impact on later developments in science and technology as Faraday. As a young man, Faraday served as assistant to Sir Humphry Davy, the great chemist. Eventually, Faraday made important chemical discoveries on his own. He isolated benzene, an organic compound, and described its molecular structure. He was the first to synthesize compounds out of the elements carbon and chlorine.

In the 1820's, however, Faraday turned his affention to electricity and magnetism. These topics became the scientific passion of his life. Faraday is most remembered for his work wit~ them. Jwo physicists had made important discoveries about electricity in the early 1820's. Physicist Hans Christian Oersted, a Dane, discovered that electrical current flowing through a wire produces a magnetic field around the wire. Then, French physicist Andre-Mane Ampere found that the magnetic field produced in this way is circular. As a result, the field around a current-carrying wire has the shape of a cylinder. A cylinder is a type of circular shape in space, like a can or a tube.
Faraday extended this understanding of electricity and magnetism. He speculated that a magnetic pole would move constantly in a circular path through the electromagnetic field around a current-carrying wire. Faraday proved this idea experimentally. He developed a device in which a magnet is left free at one end to rotate around a wire when current is applied. Faraday's experiment worked as he had suspected-and also demonstrated for the first time the principle of the electric motor. Faraday's next important discovery--of electrical induction-came in 1831. When a current is started in a wire, the process is called electromagnetic induction. Faraday found that the current could be started, or induced, by moving a magnet in and out of a coil of wire. This discovery several months earlier. But Faraday published his results first. Faraday had a strong interest in the theoretical aspects of science. He was dissatisfied with making such discoveries as electromagnetic induction without also understanding thE underlying physics. To this end he devoted much of his scientific career. Although he never completely worked out electromagnetic theory, his ideas deeply influenced later physicists. Many scientists of Faraday's time thought that electricity is a liquidlike substance that flows through wires just as water flows through pipes. Faraday, however, gradually developed radically different ideas. He believed that electricity was caused by build-up of tension or strain in maffer. The tension increases to a breaking point; then it is passed outward from the source. The build-up and release of tension occurs in rapid cycles, and tension is distributed in waves. Later scientific understanding would show Faraday's concept of electrical current to be remarkably accurate
In later life, Faraday further refined these ideas. He theorized on the way force fields-such as those created by electricity, magnetism, or gravity-work in space that is not occupied by maffer. These ideas laid the groundwork for later development of field theory, which considers the nature of force fields. James Clerk Maxwell, a British physicist active in the later 1800's, developed these ideas mathematically. Faraday's experimental work in electricity also led to important discoveries in electrochemistry. He discovered the mathematical relationship between electricity and the valence, that is, the combining power, of a chemical element. Faraday's law states this relationship. It gave the first clue to the existence of electrons

Michael Faraday was born in 1791 in a country village in Surrey, England. He came from a rather poor family. The Faradays belonged to a small Protestant religious group called the Sandemanians. The strict, simple piety of Faradav's childhood deeply affected his thinking throughout life. Though little opportunity was available to the child of a rural, poor blacksmith at that time, young Michael managed to get a job with a bookbinder. This proved a fortunate turn of fate, because the work enabled Faraday to get books to read. During this time, Faraday came upon a book about electricity. Thus began his lifelong interest in electricity. Unable to afford higher education, the teen-ager set up his own crude laboratory and conducted experiments. The second great stroke of fortune in Faradays youth was to become acquainted with the chemist Sir Humphry Davy. A combination of Faradays own persistent efforts and good luck led to his appointment as Davy's assistant in 1813. Faraday was a lilile over 20 years old at the time. This marked the beginning of a long, productive scientific career for the young man. In addition to his experimental work, Faraday became one of the most popular lecturers of his day. Tragically, during the last decade or so of his life, Faraday sank into senility, a condition in which one's mental powers decline. Queen Victoria provided a house for the great scientist to live out his days. Faraday died in 1867. The farad, a unit used to measure electrical capacitance, was named for him.

Wohler, Friedrich (1800-1882), German educator and chemist, born in Eschersheim (now part of Frankfurt-on-Main), and educated at the Universities of Marburg and Heidelberg. While studying medicine at Heidelberg, he became interested in chemistry and went to Stockholm to study with the Swedish chemist Baron Jons Jakob Berzelius. In 1836 he became Professor of Chemistry at the University of Gِttingen.

A pioneer in the field of organic chemistry, Wohler is famous for his synthesis of the organic compound urea. By this contribution he proved, contrary to scientific thinking of the time, that a product of the living processes of animals could be made in the laboratory from inorganic materials. Wohler also conducted important research on uric acid and the oil of bitter almonds, in collaboration with the German chemist Baron Justus von Liebig, and isolated the chemical elements aluminium and beryllium. He discovered calcium carbide and prepared acetylene from it; he also developed the method for preparing phosphorus that is in common use today. He wrote a number of textbooks on organic and inorganic chemistry.

Kekule Von Stradonitz, Friedrich August (1829-1896) was a German chemist who laid the foundations of modern organic chemistry. Organic chemistry is the field of research and industry that is concerned with chemical compounds based on carbon. Because of its particular atomic structure, carbon is able to form a tremendous number and variety of compounds. Carbon atoms can link with other carbon atoms as well as with atoms of other elements. Carbon often bonds with hydrogen, oxygen, nitrogen, or various combinations of these elements. All life as we know it is based on organic chemistry. Also, all the fossil fuels that we use are organic compounds. So are many medicines, including penicillin, for instance. Today, chemical research laboratories constantly synthesize, that is, make, new organic compounds. These are used for many purposes, from plastics to insect-killing substances.

Kekule' discovered several important principles of organic chemistry. First, he realized that the carbon atom is tetravalent; that is, it has four valences. A valence is the ability of one electron of an atom to combine with free electrons of other atoms. Thus, carbon has four such free electrons. Kekule' also understood that the four valences in a carbon atom are spread evenly apart. As a result, the structure of the carbon atom can be imagined as a tetrahedron (a pyramid with equal sides). This idea is helpful when examining the structure of organic compounds.

From these insights, Kekule' concluded that carbon and other elements bond together to form long chains of molecules. Kekule' then applied his new understanding to the study of benzene, an organic substance. Kekule' tried tc determine the chemical structure of benzene. He grappled with this problem with little success. Then one night in a dream, he saw the benzene molecule as a snake chasing its tail in a circle. When he woke up, Kekule' knew he had the solution for benzene's molecular structure: it is shaped like a ring. This story that often been quoted as a striking example of the subconscious (dreaming) mind helping the conscious (waking) mind solve a problem. Kekule's solution of benzene structure opened new avenues of study and research in organic chemistry.

Maxwell, James Clerk (1831-1879) was one of the greatest physicists in history. Like another great British physicist, Sir Isaac Newton, he investigated many different areas of physical science. Also like Newton, he contributed theories that opened new avenues of thought and scientific development
Maxwell's work on electricity, magnetism, and force fields was his greatest achievement. In this area of research, he built on theories that Michael Faraday had developed. Maxwell and Faraday exchanged ideas on this subject (Faraday died in 1867.) Faraday studied the electromagnetic force field produced by electrical current He became convinced that the forces at work in such a field are not confined to the conductor The conductor is, rather, simply a medium through which the force is exerted. The logical conclusion of this idea is that lines of force extend into the space that surrounds a conductor. Faraday's idea was an original and important one. But he was not able to work it out completely.
Maxwell took Faraday's idea and developed it into a complete electromagnetic theory This theory explains how electrical current radiates energy-such as radio waves and microwaves-into space. Eventually the electromagnetic theory was applied to the physical properties of radioactive materials and the energy they produce and to other types of energy as well. Maxwell then applied principles of electromagnetic theory to light. He discovered that light behaves in the same way as electromagnetic forces and concluded that light is a type of electromagnetic force.Several years later, in the 1880's, the German physicist Heinrich Hertz produced radio waves in a laboratory selling. Hertz's experiments completely confirmed Maxwell's electromagnetic theory

The importance of Maxwell's electromagnetic theory can hardly be overestimated. For the most part, twentieth century technology would have been impossible without it. Inventions such as television, radio, radar, satellite communications, and many others are a result of electromagnetic theory. In fact, communications as we know them would be unthinkable without Maxwell's pioneering work And without the long-distance communications made possible by electromagnetic waves, there would be no space exploration.
Furthermore, Maxwell's work laid the theoretical foundations for an avalanche of scientific developments to come. Development of the quantum theory-probably the most important scientific theory of our century-is partly an outgrowth of Maxwell's study of light and other electromagnetic energy. His development of field theory-the study of force fields created by magnetism, electricity, or other natural forces-also strongly influenced later physicists. Albert Einstein, for example, spent much of his later life trying to formulate a unified field theory that would explain all forces in the universe in unified, mathematical terms. This work, which continues today, would have been impossible without Maxwell's basic theories. Maxwell made important contributions to other areas of science. He developed a kinetic theory of gases that helped clarify the nature of gases. In this theory, Maxwell explained the behavior of a gas in terms of the movement of its molecules. He calculated mathematically the movements of the molecules and showed how these individual movements, multiplied billions of times, explained many properties of gases. This work enabled chemists to determine mathematically-and to predict-the characteristics of a gas.
Maxwell developed a theory of color vision and made one of the first color photographs. He also studied the rings of the planet Saturn. Maxwell studied the work of contemporary and previous scientists and learned from them. He was particularly interested in the work of Henry Cavendish, a great English scientist of the 1700's who had been largely ignored in his own time. Maxwell drew on Cavendish's work with electricity in formulating his own theories. Maxwell also tried to draw public attention to the scientific achievements of Cavendish, who had died in 1810. He published in 1879 some of the scientific papers by Cavendish on electricity.

In the early 1870's, descendants of Henry Cavendish endowed a scientific laboratory at Cambridge University. James Clerk Maxwell accepted the invitation to become the first Cavendish professor of physics. He designed the laboratory and recruited its staff. Maxwell's published scientific writings include Theory of Heat and Treatise on Electricity and Magnetism.

Mendeleyev, Dmitry Ivanovich (1834-1907), Russian chemist, best known for his development of the periodic table of the properties of the chemical elements. This table displays a periodicity (regular pattern) in the elements' properties when they are arranged according to atomic weight.

Mendeleyev was born in Tobolsk, Siberia. He studied chemistry at the University of St Petersburg, and in 1859 he was sent to study at the University of Heidelberg. There he met the Italian chemist Stanislao Cannizzaro, whose views on atomic weight (see Atom) influenced his thinking. Mendeleyev returned to St Petersburg and became Professor of Chemistry at the Technical Institute in 1863. He became Professor of General Chemistry at the University of St Petersburg in 1866. Mendeleyev was a renowned teacher, and, because no good textbook in chemistry was available, he wrote the two-volume Principles of Chemistry (1868-1870), which became a classic.

During the writing of this book, Mendeleyev tried to classify the elements according to their chemical properties. In 1869 he published his first version of what became known as the periodic table. In 1871 he published an improved version of the periodic table, in which he left gaps for elements that were not yet known. His chart and theories gained increased acceptance when three predicted elements—gallium, germanium, and scandium—were subsequently discovered.

Mendeleyev's investigations also included the study of the chemical theory of solution, the thermal expansion of liquids, and the nature of petroleum. In 1887 he undertook a solo balloon flight to study a solar eclipse.

In 1890 he resigned from the university as a consequence of his progressive political views and his advocacy of social reforms. In 1893 he became director of the Bureau of Weights and Measures in St Petersburg and held this position until his death.

Gibbs, Josiah Josiah (1839-1903) was perhaps the greatest U.S. scientist before 1900. Although not understood or appreciated by his contemporaries, Gibbs made important contributions to the science of thermodynamics. Thermodynamics deals with forms of energy and conversion of energy from one form to another. The principles of thermodynamics can be applied to many uses. One use is the study of efficiency in machines. Another application of thermodynamics is the calculation of energy loss or gain in chemical reactions.
Gibbs applied the principles of thermodynamics to physical chemistry. His work in this field has earned him the nickname, "the father of modern physical chemistry." One of Gibbs' most important contributions was his formulation of the phase rule. This is a logical description of the physical relationships among the different states of a substance, such as water, ice, and water vapor. Gibbs' most famous written work is On the Equilibrium ofHeterogeneous Substances, published between 1875 and 1878 in the Transactions of the Connecticut Academy

One of the great scientists of the age, physicist James Clerk Maxwell in England, recognized Josiah Gibbs' genius. But few Americans thought highly of him. Josiah Gibbs was born into an academic New England family. His father was a professor at Yale University in New Haven, Connecticut Josiah himself attended Yale University and in 1863 won the first doctorate of engineering awarded in the United States. After ex tended travels in Europe in the late 1860's, Gibbs returned to a professorship at Yale. There he spent the remaining years of his professional life.

Becquerel, Antoine Henri (1852-1908), French physicist and Nobel laureate, who discovered radioactivity in uranium. He was the son of Alexandre Becquerel, who studied light and phosphorescence and invented the phosphoroscope, and grandson of Antoine César Becquerel, one of the founders of electrochemistry.

Born in Paris, Becquerel became Professor of Physics at the Museum of Natural History in 1892 and at the école Polytechnique in 1895. In 1896 he accidentally discovered the phenomenon of radioactivity in the course of his research on fluorescence. After placing uranium salts on a photographic plate in a dark area, Becquerel found that the plate had become blackened. This proved that uranium must give off its own energy, which later became known as radioactivity.

Becquerel also conducted important research on phosphorescence, spectroscopy, and the absorption of light. In 1903 Becquerel shared the Nobel Prize for Physics with the French physicists Pierre Curie and Marie Curie for their work on radioactivity, a term Marie Curie coined. His works include Recherches sur la phosphorescence (Research on Phosphorescence, 1882-1897) and Découverte des radiations invisibles émises par l'uranium (Discovery of the Invisible Radiation Emitted by Uranium, 1896-1897).

Ostwald, Wilhelm (1853-1932), German physical chemist and Nobel laureate, considered one of the founders of modern physical chemistry. He was born in Riga, Latvia, and educated at the University of Dorpat (now Tartu State University). In 1881 he was appointed Professor of the Riga Polytechnic Institute and from 1887 to 1906 served as Professor of Physical Chemistry and director of the chemical laboratory at the University of Leipzig, Germany.

Ostwald is especially known for his contributions to the field of electrochemistry, including important studies of the electrical conductivity and electrolytic dissociation of organic acids. He invented a viscometer that is still used for measuring the viscosity of solutions. In 1900 he discovered a method of preparing nitric acid by oxidizing ammonia. This method, known as the Ostwald process, was used by Germany during World War I for manufacturing explosives after the Allied blockade had cut off the regular German supply of nitrates, and it is still used.

Ostwald received the 1909 Nobel Prize for Chemistry. His works include Natural Philosophy (1902; trans. 1910) and Colour Science (1923; trans. 1931). Also a famous scientist, his son, Wolfgang Ostwald, is generally regarded as the founder of colloid chemistry.

Thomson, Sir Joseph John (1856-1940) was the British physicist who discovered the electron, a fundamental atomic particle. Thomson received the 1906 Nobel Prize in physics for this work. In the middle 1890's, Thomson conducted a series of experiments on cathode rays. These rays are produced in a vacuum tube equipped with a positive terminal (anode) and a negative terminal (cathode). The cathode rays result when high-voltage electrical current is supplied to the cathode.

Thomson believed that cathode rays were actually streams of tiny charged particles. He devised experiments to deflect, or bend, the cathode rays from their normal path in the tube. Then he worked out mathematical calculations on the experimental data. Thomson concluded that the rays were indeed composed of tiny charged particles, which he named "corpuscles." Later, the name "electron" was adopted. Thomson demonstrated that the particles are negatively charged, can generate heat, and have very little mass-about 1,000 times less mass than a hydrogen ion (proton), in fact. Furthermore Thomson showed through repeated experiments that electrons are present in many chemical elements. And he theorized (correctly) that electrons are a fundamental part of all matter
Thomson's discovery revolutionized scientific understanding of the atom. Before Thomson, most scientists had believed that the atom was indivisible, the smallest particle of matter that could exist His work proved that the atom could indeed be broken down into smaller particles. For this reason, Thomson can be considered the founder of modern atomic physics. Based on his work with electrons, Thomson proposed an atomic model. He suggested that the atom is a sphere (a round ball) with the electrons embedded throughout its inner volume. According to Thomson's model, the interior of an atom would resemble a watermelon with embedded seeds. Within the following 20 years, however, physicists Ernest Rutherford and Niels Bohr would develop a more workable atomic model.
Thomson discovered the first isotopes of a chemical element, specifically of the element neon. An isotope is a form of a chemical element that has a different atomic weight than the element in its normal form. Later, a pupil of Thomson, Francis Aston, invented the mass spectrograph. This device separates atoms of differing atomic weights in a substance. In 1903 Thomson proposed a discontinuous theory of light. By this, Thomson meant that light rays are composed of separate particles rather than continuous streams. Several years later, Einstein developed the photon theory of light This theory proposes that light is made up of packets of energy called photon£

Thomson had a great impact on the field of atomic physics as a teacher. He was director of the Cavendish Laboratory at Cambridge University for the eventful years in the 1890's and early 1900's. During this period, modern atomic physics came into being.

Planck, Max (1858-1947) proposed the quantum theory in 1900 to explain how radiant energy (such as light) is given off and absorbed. The quantum theory completely revolutionized modern physics. It answered many questions and solved many problems that had puzzled scientists for years. For his work with the quantum theory, Planck won the Nobel Prize in physics in 1918.

The basic concept of the quantum theory is that radiant energy, such as light, is a continuous stream of tiny packets of energy called quanta (or quantum in the singular). A quantum is the smallest amount of energy possible. Mathematically, the energy in a quantum is measured as the frequency of the radiation, V, times a universal constant, h. This constant value is also known as Planck's constant. Planck's formula applies to all forms of radiant energy, including ultraviolet light, X rays, radio waves, microwaves, and so on. An obvious conclusion that can be drawn from Planck's theory (and formula) is that forms of radiant energy with high frequencies have higher energy than those with lower frequencies. Planck proposed his theory to solve a particular experimental problem. He never expected it to become the basic principle of a new kind of physics. But this is exactly what happened. Albert Einstein and Niels Bohr quickly adopted Planck's ideas and extended them to many areas of physics. Einstein used the quantum theory to explain the photoelectric effect Bohr used the theory to explain how electrons in the outer shells of their atoms give off light energy without falling back into the nucleus. He theorized that electrons give off energy in limited bursts of quanta-not continuously.
Max Planck was born in Kiel, a city in north - western Germany, in 1858. He studied at the universities of Munich and Berlin with the great German scientists Hermann Helmholtz and Gustav Kirchhoff. Planck received a Ph.D. in physics and began teaching physics at the university level. He taught at the University of Berlin for most of his career. Planck served in many scientific associations, including the Prussian Academy of Science and the Kaiser Wilhelm Society of Berlin (later renamed the Max Planck Society). He was also made a foreign member of the Royal Society of London.

Planck enjoyed a wide range of interests outside of physics, including music, religion, and philosophy. He was also deeply concerned about justice. Planck stayed in Germany during the Nazi regime because he felt his duty to do so. But his family suffered terribly. In 1944 his son Erwin was arrested and executed for alleged participation in the plot to assassinate Hitler. Planck remained in Germany after World War II. He died in 1947.

Curie, Pierre (1859-1906), French physicist and Nobel laureate, best known for his work on radioactivity with his wife, Marie Curie. Pierre Curie was born in Paris and educated at home by his parents. He then studied physics at the Sorbonne. His interest turned to crystallography and in 1877, with his brother Jacques, he discovered piezoelectricity. Curie taught physics at a number of institutions before being appointed Professor at the Sorbonne in 1904. Until the mid-1890s most of Curie’s research was on magnetism and on crystals.

In 1894 he met Marie Sklodowska at the Sorbonne and married her the following year. Her subsequent research followed up the discovery of X-rays in 1895 by Wilhelm Roentgen and the discovery by Antoine Becquerel in 1896 of the emission of similarly penetrating rays from uranium. She found that these latter rays were also produced by the uranium ore pitchblende, but in quantities too great to be accounted for by the uranium alone. To help his wife to isolate the element that must be producing the bulk of these rays, Pierre Curie gave up his own research. In the course of this work they discovered and named the radioactive elements polonium and radium. For this they jointly received, with Becquerel, the Nobel Prize for Physics in 1903. They continued their joint work on radioactivity, but in 1906 Pierre Curie was killed in a road accident in Paris.

Arrhenius, Svante August (1859-1927), Swedish chemist, who helped lay the foundations of modern chemistry. Born near Uppsala, he was educated at the University of Uppsala and received his Ph.D. in 1884. While still a student, he studied the conductive properties of electrolytic (charge-conducting) solutions. In his doctoral thesis he formulated the theory of electrolytic dissociation. This theory holds that in electrolytic solutions, the dissolved chemical compounds in the solution are dissociated into ions, even when there is no current flowing through the solution. Arrhenius also postulated that the degree of dissociation increases as the solution becomes more dilute, a hypothesis that later turned out to be true only for weak electrolytes. His theory was initially thought to be wrong, and his thesis was given the lowest possible passing grade. Later, however, Arrhenius's theory of electrolytic dissociation became generally accepted, and eventually became one of the cornerstones of modern physical chemistry and electrochemistry.

In 1889 Arrhenius also observed that the speed of chemical reactions increases markedly when the temperature is increased, at a rate proportional to the concentration of the activated molecules. Arrhenius became Professor of Chemistry at the University of Stockholm in 1895 and Director of the Nobel Institute of Physical Chemistry in 1905. His awards and honours include the 1903 Nobel Prize for Chemistry. He wrote works on physical and biological chemistry, electrochemistry, and astronomy. In astronomy he is noted for his suggestion that life on Earth originated from living spores driven through space by the pressure of light. (See Ionization).

Curie, Marie, née Maria Sklodowska (1867-1934), French physicist and twice Nobel laureate, best known for her work on radioactivity, with her husband Pierre. Maria Sklodowska was born in Warsaw, Poland, which was then part of the Russian Empire. Her father, an ardent Polish nationalist, taught mathematics and physics at a secondary school, but was denied promotion because of his political views, which he passed on to his daughter. She won a gold medal at school and then participated in the “underground” university, which aimed at maintaining Polish culture in the face of Russian domination. There she was influenced by the high esteem in which its members held science. She found employment as a governess before joining her sister in Paris in 1891. She continued her scientific studies at the Sorbonne, where she came first in physics in 1893. In 1894 she met Pierre Curie, whom she married the following year.

Following the discovery of X-rays by Wilhelm Roentgen and the discovery of the emission of novel radiations from uranium in 1896 by Antoine Becquerel, Marie Curie turned her attention to the question of whether there were any other elements that emitted these rays. In 1898 she discovered that such rays were emitted in unexpected strength by the uranium-containing mineral pitchblende, for which she coined the term “radioactive”. Her observations led her to conclude that there was a previously unknown chemical element in the pitchblende. Both the Curies then made a Herculean effort to reduce the pitchblende chemically, repeatedly dissolving it and crystallizing it out to concentrate the unknown component. In the end they obtained a few hundredths of a gram containing the source of the radiation. From the spectrum of this material they confirmed the existence of a new element, which they named polonium after Marie Curie’s homeland. In further confirmatory experiments they found a second highly radioactive element, which they named radium. It was not until 1902 that they isolated chemically a sample of radium.

In 1903 the Curies were jointly awarded, with Becquerel, the Nobel Prize for Physics. In 1906 Pierre Curie was killed in a road accident. Thereafter Marie Curie took over Pierre’s chair, becoming the first woman to teach at the Sorbonne. She continued her theoretical work on radioactivity, introducing into physics the terms “disintegration” (the breakdown of an atom in radioactivity) and “transmutation” (the radioactive alteration of an atom into an atom of a different element). In 1911 she won the Nobel Prize for Chemistry.

During World War I Curie played an active role in the use of radiation for medical purposes, an interest that became dominant thereafter. She became perhaps the most famous woman in the world, a reputation about which she had mixed feelings, since it interfered with her scientific work, which for her always came first. However, she was able to use her fame to promote the medical uses of radium, by facilitating the foundation of radium therapy institutes in France, Poland, the United States, and elsewhere. She was thus able to give concrete expression to her belief in the value of science to humanity, a belief that she had held since her days in the Polish underground university.

Throughout the 1920s Marie Curie’s health declined and she had to have several cataract operations. Because of lack of knowledge about the dangers of radioactivity, she had been exposed during her career to massive doses of radiation. In 1934, as a consequence of this, she died of aplastic anaemia in an Alpine sanatorium.

Haber, Fritz (1868-1934), German chemist and Nobel laureate, best known for his development of an economical method of ammonia synthesis. Haber was born in Breslau (now Wroclaw, Poland) and educated at the Technische Hochschule in Berlin. He was appointed Professor of Physical Chemistry at the University of Berlin in 1911. Subsequently he became director of the Kaiser Wilhelm Institute for Physical Chemistry in Berlin.

During World War I Haber was chief of the German chemical warfare service, and he directed the chlorine gas attack at the second Battle of Ypres. In 1933, because of anti-Semitic policies in Germany, Haber resigned and went to Switzerland, where he died the following year.

Haber's greatest achievement was his discovery in 1913 of a process for synthesizing ammonia by the direct combination of nitrogen and hydrogen (see Nitrogen Fixation). The method was adapted to commercial use in the 1930s by the German chemist Karl Bosch. The Haber-Bosch process is used in the manufacture of explosives and in the production of fertilizers. Haber also made fundamental contributions to the field of electrochemistry. He was awarded the 1918 Nobel Prize for Chemistry.

Rutherford, Ernest, 1st Baron Rutherford of Nelson and Cambridge (1871-1937), British physicist, who became a Nobel laureate for his pioneering work in nuclear physics and for his theory of the structure of the atom.

Rutherford was born on August 30, 1871, in Nelson, New Zealand, and was educated at the University of New Zealand and the University of Cambridge. He was Professor of Physics at McGill University in Montreal, Quebec, from 1898 to 1907 and at the University of Manchester in England during the following 12 years. After 1919 he was Professor of Experimental Physics and director of the Cavendish Laboratory at the University of Cambridge and also held a professorship, after 1920, at the Royal Institution of Great Britain in London.

Rutherford was one of the first and most important researchers in nuclear physics. Soon after the discovery of radioactivity in 1896 by the French physicist Antoine Henri Becquerel, Rutherford identified the three main components of radiation and named them alpha, beta, and gamma rays. He also showed that alpha particles are helium nuclei. His study of radiation led to his formulation of a theory of atomic structure, which was the first to describe the atom as a dense nucleus which electrons circle.

In 1919 Rutherford conducted an important experiment in nuclear physics when he bombarded nitrogen gas with alpha particles and obtained atoms of an isotope of oxygen and protons. This transmutation of nitrogen into oxygen was the first artificially induced nuclear reaction. It inspired the intensive research of later scientists on other nuclear transformations and on the nature and properties of radiation. Rutherford and the British physicist Frederick Soddy developed the explanation of radioactivity that scientists accept today. The rutherford, a unit of radioactivity, was named in his honour.

Rutherford was elected a fellow of the Royal Society in 1903 and served as president of that institution from 1925 to 1930. He was awarded the 1908 Nobel Prize for Chemistry, was knighted in 1914, and was made a baron in 1931. He died in London on October 19, 1937, and was buried in Westminster Abbey. His writings include Radioactivity (1904); Radiations from Radioactive Substances (1930), which he wrote with the physicists Sir James Chadwick and Charles Drummond Ellis, and which has become a standard text; and The Newer Alchemy (1937).

Soddy, Frederick (1877-1956), British chemist and Nobel laureate. Soddy was born in Eastbourne, Sussex, and educated at Eastbourne College, the University College of Wales, and the University of Oxford. He was a lecturer in physical chemistry and radioactivity at the University of Glasgow from 1904 to 1914 and Professor of Chemistry at Oxford from 1919 to 1936, at which time he retired from academic life.

With the physicist Ernest Rutherford he began investigating radioactive transformations of atomic nuclei and eventually developed a theory of atomic structure. Soddy is particularly known for his investigations of the origin and nature of isotopes, for which he was awarded the 1921 Nobel Prize for Chemistry. His writings include such classic scientific works as Radioactivity (1904), Interpretation of the Atom (1932), The Story of Atomic Energy (1949), and Atomic Transmutation (1953), and works of a political-economic nature, including Cartesian Economics (1922), and Role of Money (1934).

Meitner, Lise (1878-1968), Austrian-Swedish physicist, who first identified nuclear fission. She was born in Vienna and educated at the Universities of Vienna and Berlin. In association with Otto Hahn, she helped discover the element protactinium in 1918, and was a Professor of Physics at the University of Berlin from 1926 to 1933. In 1938 she left Germany and joined the atomic research staff at the University of Stockholm. In 1939 Meitner published the first paper concerning nuclear fission. She is also known for her research on atomic theory and radioactivity. In her work she predicted the existence of the chain reaction, which contributed to the development of the atomic bomb. In 1946 she was visiting professor at Catholic University in Washington, D. C., and in 1959 she revisited the United States to lecture at Bryn Mawr College.

Einstein, Albert (1879-1955) was one of the greatest scientists and most creative minds of all time. Before he was 30 years old, Einstein had published a group of brilliant theories that completely changed modern science. His theories provided basic knowledge needed to unleash the power of the atom. Einstein urged the United States to prepare to stop Nazi Germany by developing an atomic weapon. Then, after the Nazi threat was gone, he urged nations to join together in a world government that would, he believed, use atomic power responsibly.

Einstein revealed several of his earth-shaking theories in the single year of 1905. He presented his ideas in three scientific papers published in Annals o Physics, a German physics journal. One of the papers of 1905 was entitled, "On a Heuristic Viewpoint Concerning the Production and Transformation of Light." Einstein suggested that light could be thought of as a stream of tiny particles, called quanta. For this. reason, light demonstrates qualities of both waves and particles. Einstein's ideas about light laid important groundwork for the quantum theory of physics. The quantum theory would become, in a short time, a revolutionary way of thinking about motion at the atomic level. Einstein also explained the photoelectric effect. This occurs when a bright beam of light strikes certain metal, causing the metal to release electrons in the form of an electrical current Einstein's work made possible the development of the photoelectric cell, also called the electric eye. The 1921 Nobel Prize in physics was awarded to Einstein for this work.
Another paper of 1905, "The Electrodynamics of Moving Bodies," presented Einstein's special theory of relativity. This theory introduced the following idea: given that the speed of light is constant and all natural laws are the same, then both time and motion are relative to the observer. This was a radical change in scientific thinking, because no one had yet thought that time or motion might be subjective, that is changeable depending upon the observer's perspective. Later in the same year, Einstein published another closely related paper. He worked out some of the mathematical ideas related to special relativity. Most importantly, he related mass to energy in a definite proportion in his famous equation, "E mc2" in which E stands for energy, m for mass, and C for the speed of light. The equation implied that an enormous amount of energy could be liberated from a relatively small amount of matter. It established the theoretical foundation for later work with atomic power.
Still another Einstein paper of 1905 was the Motion of Small Particles Suspended in Stationary Liquid." In this paper, Einstein explained the apparently random motion of tiny particles in a liquid. This type of motion is known in science as Brownian motion. Some years later, Einstein developed his theory of relativity more broadly. In 1916 he published an article entitled, "The Foundation of the General Theory of Relativity, in Annals of Physics. Einstein explained that gravitation is a curved field in the space-time continuum, rather than a force as Sir Isaac Newton had thought. Theoretically, this meant that starlight should be bent, or deflected, as it passes by the sun. But there was no immediate way to test Einstein's theory, since doing so would require observations at the time of a solar eclipse. That is the only time in which starlight is visible to observers on the earth. Proof of Einstein's general theory of relativity came in 1919. In that year, the Royal Society of London sent a scientific expedition to the Principe Island in the Gulf of Guinea to observe a solar eclipse. The sun's eclipse allowed the scientists to observe starlight passing near the sun. Their calculations verified Einstein's predictions. Confirmation of Einstein's theory of relativity brought him international and lasting fame. From this time on, Einstein belonged to the world. Moreover, the very name of Einstein became a synonym for genius. Few scientists have become as widely or as popularly known in life as Einstein. From the 1920's on, Einstein directed his scientific efforts toward finding mathematical relationships that would unify all kinds of forces, such as gravity and electromagnetism. This new field of research became known as unified field theory. Einstein's efforts in this field drew him into controversy. Many, if not most, physicists believed that the quest for a unified field theory was an impossible one. They reasoned that the movement of a single particle cannot be predicted, according to the quantum theory. For the most part, they also believed that future theoretical advances in physics would never remove this basic uncertainty principle. For these reasons, Einstein became rather isolated from the scientific community toward the end of his life. Einstein lived a very public life in his mature years. This was, in part, a result of the extraordinary fame he achieved in science. Also, world events repeatedly forced Einstein into the limelight. At various times of his life, Einstein had been a German, Swiss, and United States citizen. He had lived through the two world wars as a mature man. Furthermore, Einstein had passionate opinions on war, peace, and world government During World War I, Einstein had risked grave trouble by embracing pacifism, a belief in peace at almost any cost Einstein also supported Zionism-the movement to created a homeland for the Jewish people in Palestine. Later, he supported the state of Israel. Einstein continued to be a pacifist until Hitler gained power in Germany. In 1933 Einstein renounced his German citizenship and fled Germany. Shortly afterward, he accepted a position at Princeton University in the United States. He was to live at Princeton for the rest of his life. A group of physicists persuaded Einstein to write a letter of warning to President Roosevelt in 1939. The content of this warning was that the uranium atom had been split, and Hitler's scientists might be developing an atomic bomb. President Roosevelt took Einstein's letter-signed by several prominent scientists-quite seriously. Shortly afterward, he took steps to commit the United States to developing an atomic weapon. This was the beginning of the Manhaflan project and the bombs used on Japan in 1945. Einstein himself took no part in the project Ironically, he learned of the atomic attacks against Hiroshima and Nagasaki in August, 1945, in the same ways as most Americans-through radio and newspapers. Always a public figure, Einstein joined with other scientists in urging the responsible use of atomic energy. Einstein had a particular vision of a peaceful postwar era. He wanted the former Allies-the United States, Britain, and the Soviet Union-to establishes a world government. Such a government, believed Einstein, would have the authority to control the use of atomic power. By the late 1940's, a bitter cold war had developed between the United States and the Soviet Union. Einstein's hopes for world unity were dashed. Nevertheless, Einstein continued his work in physics with unified field theory. He published a version of the theory in 1950.

Albert Einstein was born in southern Germany in 1879. As a boy, Einstein went to the rigid, harsh German schools of the late 1800's. Young Albert showed little scholastic ability. Meanwhile, he studied the violin with his Uncle Jacob. Thus, Einstein began a lifelong enjoyment of music as a very good amateur violinist. Einstein later said that music first stimulated his fascination with mathematics. In 1900 Einstein graduated from the Swiss Polytechnic Academy in Zurich, Switzerland and became a Swiss citizen. A short time later he married and got a job at the Swiss Patent Office. Einstein published his famous scientific papers in 1905. Einstein's astonishing theories earned him respect from the scientific community. He won teaching positions at European universities, first at Prague, then Zurich. and finally at Berlin in 1914. During this time Einstein was separated from his wife and family by the outbreak of war. The separation led to the couple's divorce. After the war, Einstein married his cousin EIsa. She remained with him until her death in 1936.

Hahn, Otto (1879-1968), German physical chemist and Nobel laureate, whose greatest contributions were in the field of radioactivity. Hahn was born in Frankfurt-on-Main and educated at the Universities of Marburg and Munich. In 1911 he became a member of the Kaiser Wilhelm Institute for Physical Chemistry in Berlin and served as director of the institute from 1928 to 1945, when it was taken into Allied custody after World War II. In 1918 he discovered, with the Austrian physicist Lise Meitner, the element protactinium. Hahn, with his co-workers Meitner and the German chemist Fritz Strassmann, continued the research started by the Italian physicist Enrico Fermi in bombarding uranium with neutrons. Until 1939 scientists believed that elements with atomic numbers higher than 92 (known as transuranic elements) were formed when uranium was bombarded with neutrons. In 1938, however, Hahn and Strassmann, while looking for transuranic elements in a sample of uranium that had been irradiated with neutrons, found traces of the element barium. This discovery, announced in 1939, was irrefutable evidence, confirmed by calculations of the energies involved in the reaction, that the uranium had undergone fission, splitting into smaller fragments consisting of lighter elements. Hahn was awarded the 1944 Nobel Prize for Chemistry for his work in nuclear fission. It was proposed in 1970 that the newly synthesized element number 105 be named hahnium in his honour, but another naming system was adopted for transuranic elements beyond 104.

Bohr, Niels Henrik David (1885-1962), Danish physicist and Nobel laureate, who made basic contributions to nuclear physics and the understanding of atomic structure.

Bohr was born in Copenhagen on October 7, 1885, the son of a physiology professor, and was educated at the University of Copenhagen, where he earned his doctorate in 1911. That same year he went to the University of Cambridge in England to study nuclear physics under J. J. Thomson, but he soon moved to the University of Manchester to work with Ernest Rutherford.

Bohr's theory of atomic structure, for which he received the Nobel Prize for Physics in 1922, was published in papers between 1913 and 1915. His work drew on Rutherford's nuclear model of the atom, in which the atom is seen as a compact nucleus surrounded by a swarm of much lighter electrons. Bohr's atomic model made use of quantum theory and the Planck constant (the ratio between quantum size and radiation frequency). The model posits that an atom emits electromagnetic radiation only when an electron in the atom jumps from one quantum level to another. This model contributed enormously to future developments of theoretical atomic physics.

In 1916 Bohr returned to the University of Copenhagen as a Professor of Physics, and in 1920 he was made Director of the university's newly formed Institute for Theoretical Physics. There Bohr developed a theory relating quantum numbers to large systems that follow classical laws, and made other major contributions to theoretical physics. His work helped lead to the concept that electrons exist in shells and that the electrons in the outermost shell determine an atom's chemical properties. He also served as a visiting professor at many universities.

In 1939, recognizing the significance of the fission experiments of the German scientists Otto Hahn and Fritz Strassmann, Bohr convinced physicists at a scientific conference in the United States of the importance of those experiments. He later demonstrated that uranium-235 is the particular isotope of uranium that undergoes nuclear fission. Bohr then returned to Denmark, where he was forced to remain after the German occupation of the country in 1940. Eventually, however, he escaped to Sweden, in peril of his life and that of his family. From Sweden the Bohrs travelled to England and eventually to the United States, where Bohr joined in the effort to develop the first atomic bomb, working at Los Alamos, New Mexico, until the first bomb's detonation in 1945. He opposed complete secrecy of the project, however, and feared the consequences of this ominous new development. He desired international control.

In 1945 Bohr returned to the University of Copenhagen, where he immediately began working to develop peaceful uses for atomic energy. He organized the first Atoms for Peace Conference in Geneva, held in 1955, and two years later he received the first Atoms for Peace Award. Bohr died in Copenhagen on November 18, 1962.

Moseley, Henry Gwyn Jeffreys (1887-1915), English experimental physicist who achieved the first experimental identification of the atomic number and nuclear charge of an element. Born in Weymouth, Dorset, Moseley came from a distinguished family of scientists. After studying physics at Oxford, he joined Ernest Rutherford at Manchester. His initial work was on beta emission from radium, but he soon moved on to the study of X-ray spectra, using the technique of X-ray diffraction developed by W. H. Bragg and his son, W. L. Bragg. Ever since Mendeleev's proposal of the periodic table in 1869, chemists had striven to explain the fact that the chemical properties of the elements are a periodic function of their atomic weights. By means of X-ray diffraction, Moseley established, in 1913, a relationship between the frequencies of X-ray emission lines and what he concluded must be the atom's nuclear charge, thereby confirming the suggestion of A. van der Broek that the nuclear charge indicated an element's position in the periodic table. Moseley thus provided an experimental basis for equating nuclear charge with what he called atomic number. From now on it became possible to predict, from gaps in the series of X-ray frequencies, the existence of missing elements in the periodic table. Moseley moved back to Oxford to continue his work there, but was killed two years later in the battle of Sari Bair during the Gallipoli campaign.

Chadwick, Sir James (1891-1974), British physicist and Nobel laureate, who is best known for his discovery in 1932 of one of the fundamental particles of matter, the neutron, a discovery that led directly to nuclear fission and the atomic bomb. He was born in Manchester and educated there at Victoria University. In 1909 he began working under the physicist Ernest Rutherford. At the end of World War I he went to the University of Cambridge with Rutherford, with whom he continued a fruitful collaboration until 1935. In that year Chadwick became professor at the University of Liverpool. From 1948 to 1958 he was Master, and from 1959 a Fellow, of Gonville and Caius College, University of Cambridge.

Chadwick was one of the first in Britain to stress the possibility of the development of an atomic bomb and was the chief scientist associated with the British atomic bomb effort. He spent much of his time from 1943 to 1945 in the United States, principally at the Los Alamos Scientific Laboratory (now the Los Alamos National Laboratory), New Mexico. A Fellow of the Royal Society, Chadwick received the 1935 Nobel Prize for Physics and was knighted in 1945.

De Broglie, Louis Victor (1892-1987), a French physicist, proposed the theory explaining the wave properties of electrons in 1924. His work greatly advanced the early understanding of quantum theory, the study of the parts of the atom and their behavior. In 1924, existing quantum theory stated that light waves sometimes behave like particles. Using mathematical logic, de Broglie reasoned that the particles, in turn, have wavelike properties. De Broglie's theory of "matter waves," which sent physicists everywhere thinking in new and unexpected direction, became the foundation for a new field of study-wave mechanics.

Proof of de Broglie's theory came in 1927 in experiments by physicists Clinton j. Davisson and Lester Halbert Germer, working with slow electrons, and by G. P. Thomson, working with fast electrons. For his vision, de Broglie received the 1929 Nobel Prize for physics and the Henri Poincare Medal of the Academie des Sciences. After receiving a degree in history from the Sorbonne in 1909, de Broglie took up his real interest, receiving a "license" in science from the University of Paris in 1913. During World War 1(1914-1918), he served in the radiotelegraph branch of the French Engineering Corps at the wireless station of the Eiffel Tower. Afterward, de Brogue resumed his scientific study at his brother's physics laboratory. Born into a noble French family, de Broglie was known as Prince Louis Victor Pierre Raymond de Broglie throughout his life. His ancestors served French kings in war and diplomacy from the time of Louis XIV. De Broglie's brother Maurice, also a physicist, was known for his research in nuclear physics, X rays, and radioactivity. While pursuing his lifelong interest in research, de Broglie taught theoretical physics at the Henri Poincare' Institute in Paris. In 1943, he founded the Center for Studies in Applied Mathematics at the institute to help physicists and mathematicians work together. Along with his brother, de Broglie was named to the French High Commission on Atomic Energy in 1945, and he also was a member of the Academie Francaise, which oversees French language and literature. De Broglie was elected to a number of prestigious international scientific societies and was appointed permanent secretary of the French Academy of Sciences in 1942.

Hall, Lioyd Augustus (1894-1971) was an African American chemist and inventor. He was granted more than 100 patents for processes used in food manufacturing and packaging, including his development of curing salts, condiments, spices, and flavors used in the meatpacking industry.
Born in Elgin, Illinois, Hall received a B.S. degree in 1916 from Northwestern University. He worked briefly as a sanitary chemist at the Chicago Board of Health and as president and chemical director of Chemical Products Corporation. He then served as chief chemist and director of research at Grifrith Laboratories Inc. in Chicago from 1925 to 1946. Hall, a member of several professional societies, was the first African American to serve on the Board of Directors of the American Institute of Chemists, which presented him with its Honor Scroll Award of the Institute's Chicago Chapter in 1956. He also served on the board of the Institute of Food Technologists, which he co founded.

Julian, Percy Lavon (1899-1975), an African American research chemist, created a long list of useful products, including synthetic forms of the hormones progesterone, testosterone, and cortisone, as well as physostigmine, a drug used to treat glaucoma. Julian owned over 100 patents, many for products derived from soybeans. Born in Montgomery, Alabama, Julian received a B.A. from Depauw University (1920), an M.A. from Harvard University (1923), and a Ph.D. from the University of Vienna, Austria (1931). Before and after his graduate studies at the University of Vienna, Julian held a teaching position at Howard University. Later, he taught and continued his research at DePauw.
Julian's early research efforts focused on creating a synthetic version of physostigmine. By 1935, he had created an inexpensive and easily produced synthetic copy of this drug for the treatment of glaucoma, a serious eye disease. Offered a full-time research position and the funds to support his many ideas, Julian turned to industry as chief chemist and director of research at the Glidden Company. There, Julian turned his attention to making soybean derivatives, isolating proteins to be used in the manufacture of paper coatings, fabric sizings, and water-based paints, for a start. A fire-fighting foam he developed to fight oil and gasoline fires is credited with saving countless lives during World War II(1939-1945). julian also synthesized the male and female hormones, or steroids, progesterone and testosterone. The manufactured versions of these drugs dramatically reduced the cost of vital therapies.

Julian next extracted synthetic cortisone from soybeans. People suffering from painful, crippling arthritis and a host of other ailments suddenly found that a painkilling drug, which had cost as much as $50, was now available in synthetic form for only a few cents. In 1953, Julian left Glidden to form Julian labor atones, Inc., with branches in Mexico and South America. Working with yams, he continued to focus on synthetic hormones. In 1964, he sold this business to become director of the Julian Research Institute.

Fermi, Enrico (1901-1954) was an Italian-born, Americanized physicist who made fundamental contributions to modern nuclear physics. Fermi was the first scientist to split the atom, although he did not realize what he had done at the time. Later, Fermi and his co-workers developed the first atomic weapon, which was eventually used in warfare against Japan in 1945. In 1934 Frederic and Irene Joliot-Curie produced artificial radioactivity by bombarding elements with alpha particles. Fermi wanted to build on this experimental work. He used slowed down neutrons obtained from radioactive beryllium, a chemical element, to bombard elements. This proved a very effective method to release radioactive particles from the bombarded material. When Fermi used Uranium of atomic weight as the target, however, he obtained unexpected radioactive substances. Fermi's co-workers thought the new substances might be a new element of atomic weight 93. Fermi did not claim to understand what had happened in the experiment when he reported its results. (1901-1954) was an Italian-born, Americanized physicist who made fundamental contributions to modern nuclear physics. Fermi was the first scientist to split the atom, although he did not realize what he had done at the time. Later, Fermi and his co-workers developed the first atomic weapon, which was eventually used in warfare against Japan in 1945. In 1934 Frederic and Irene Joliot-Curie produced artificial radioactivity by bombarding elements with alpha particles. Fermi wanted to build on this experimental work. He used slowed down neutrons obtained from radioactive beryllium, a chemical element, to bombard elements. This proved a very effective method to release radioactive particles from the bombarded material. When Fermi used Uranium of atomic weight as the target, however, he obtained unexpected radioactive substances. Fermi's co-workers thought the new substances might be a new element of atomic weight 93. Fermi did not claim to understand what had happened in the experiment when he reported its results.
Only years later did Fermi and the world-realize that he had in fact crossed a great threshold in history. He had been the first per son to split an atom in a way that could be controlled to harness atomic energy. (This process would later be called nuclear fission. Fermi's experiment would lead to the development of the atomic bomb and nuclear energy The importance of Fermi's discovery was confirmed by three German scientists, Otto Hahn, Lise Meitner, and Fritz Strassmann, in 1938. Lise Meitner secretly went to Stockholri where, with her nephew, Otto Frisch, she announced the Hahn group's experimental conclusions to the world in January, 1939. She explained that they had split the uranium atom into the elements barium, krypton, and small amounts of other materials. According to Einstein's famous mass-energy equation, F = mc2, nuclear fission, or splitting of the atom, could be expected to yield enormous amounts of energy. In the meantime, Enrico Fermi had gone to Stockholm in 1938 to accept the Nobel Prize i physics. Fermi and his family used this opportunity to escape from Fascist Italy, settling in the United States. In New York, Fermi heard about the conclusions of the Hahn-MeitnerStrassman research team. The experiments were repeated at Columbia University with similar results and conclusions. Based on these experiments, Danish physicist Niels Bohr suggested the possibility of a nuclear chain U' action. Other physicists considered this suggestion and settled on uranium-235 as the be candidate for such a reaction.
Meanwhile, Fermi and two other scientists Leo Szilard and Eugene Wigner, became concerned about the possibility that Hitler's scientists in Nazi Germany might achieve a chain reaction and develop an atomic weapon. This group drafted a letter to President Roosevelt. Albert Einstein signed the letter and presented it to the president on October 11, 1939. Out of this event developed the Manhattan Project, code name for a scientific team assembled in 1942 to develop an atomic bomb for the United States. Fermi was chosen to produce a nuclear chain reaction in uranium-235. He developed an atomic pile, or nuclear reactor, to produce the controlled, self-sustaining chain reaction required. On December 2, 1942, Fermi and his team produced the first such chain reaction. This event led to the successful testing of the first atomic weapon on July 16, 1945, then to the atomic bombing of Hiroshima and Nagasaki in August, 1945.

Enrico Fermi was born in Rome. By the age of 21, he had earned his doctorate from the University of Pisa. He then did graduate work under the physicist Max Born, who profoundly influenced his scientific development, at the German University of Gottingen. Afterward, he returned to the University of Florence, then to the University of Rome, where he became a full professor in theoretical physics. In 1929 the Royal Academy of Italy elected Enrico Fermi to membership, the youngest member in its ranks. In addition to the Nobel Prize, Fermi received the Congressional Medal of Merit in 1946. Two years earlier, the Fermis had become U.S. citizens. The Royal Society of London elected Fermi as a foreign member in 1950. The Enrico Fermi Award was established in his honor, and Fermi became its first recipient in 1954. An artificially produced chemical element, fermium, was named for him in 195Z. Also, the Fermi National Accelerator Laboratory, a physics research laboratory near Chicago, bears his name

Lawrence, Ernast Orlando (1901-1958), an American physicist, is the inventor of the cyclotron, a machine that accelerates atomic particles in a vacuum chamber between the poles of an electromagnet until they are traveling a terrific speeds. Lawrence received the 1939 Nobel Prize in physics for his invention of the cyclotron and the results obtained-not only physics but also in the fields of biology and medicine.
By hurling speeding atomic "bullets" the cyclotron could "smash" atoms, changing the composition of their nuclei to form new radioactive elements. Lawrence and his "atom-smasher" played a key role in the development of the atomic bomb. Lawrence organized the Los Alamos Scientific Laboratories in New Mexico, where much of the atomic bomb research was carried out A Lawrence cyclotron at Berkeley Laboratory, in California, created the uranium 235 that fueled the first atomic bomb. Another cyclotron produced the first plutonium. Lawrence's first cyclotron, built for $25 in 1930, was fashioned from window glass, brass, and sealing wax and set up on a kitchen chair. From this, he went on to build a giant machine weighing 85 tons and using the largest magnet of the time. His garage was the setting for another "first." Tinkering with spare parts in his garage to answer a question for some of his seven children, Lawrence also invented the basic patent for the color television tube.
Born in Canton, South Dakota, Lawrence attended St Olaf's College, and received his B.S. degree from the University of South Dakota in 1922. He studied at the University of Minnesota, the University of Chicago, and received his Ph.D. from Yale University in 1925. After teaching at Yale for one year, Lawrence joined the faculty of the University of California at Berkeley when he was 27 years old. By age 29, he had achieved the rank of full professor. Six years later, he became director of the radiation laboratory there. The University of California's radiation laboratory, which was established by Lawrence in 1932, continues today as a leading center in high-energy physics and life sciences research. In 1952, a second research center in Livermore, California, was established with a primary focus on the development of national security systems for the United States. Together, the two centers formed the Lawrence Radiation Laboratories. In 1971, these facilities were formally separated and named the Lawrence Berkeley Laboratory and the Lawrence Livermore National Laboratory.

After World War 11(1939-1945), Lawrence continued his research in nuclear physics. In 1957, he received the Inrico Fermi Award, the highest honor in his field. Lawrence also received many other national and international awards. He was an officer of the French Legion of Honor, an honorary member of the Academy of Science of the Soviet Union, and an honorary member of many other prestigious international scientific societies. In 1961 lawrencium, an artificially created radioactive element with an atomic number of 103, was named for him.

Pauling, Linus (1901-1994) was a brilliant American chemist and political activist who won two Nobel Prizes, one for chemistry and one for peace. Pauling was the first person since Marie Curie to win two Nobel Prizes, and the first ever to be the sole recipient. Pauling received the Nobel Prize for chemistry in 1954 for his research on the chemical bond, the fcrce that gives atoms the cohesiveness to form molecules-the building blocks of physical matter. A world-class chemist, Pauling is also credited with laying the groundwork that led other researchers to uncover the secrets of DNA (deoxyribonucleic acid), the genetic material in all living things. He narrowly narrowly missed getting a third Nobel Prize for this work.
Pauling's 1962 Nobel Peace Prize honors the other major passion of his life. The award citation praises Pauling's work not only against the testing of nuclear weapons, not only against the spread of these armaments, not only against their very use, but against all warfare as a means of solving international conflicts. Born in Portland, Oregon, Pauling dropped out of high school, refusing to take courses he saw as pointless. He was accepted without a diploma at Oregon Agriculture College, where he was quickly recognized as a prodigy, receiving a BA. degree in 1922. He earned a Ph.D. from the California Institute of Technology in 1925. As a Guggenheim Fellow (1926-1927), Pauling studied a new field of physics-quantum mechanics-with the great physicists of Europe, including Niels Bohr in Copenhagen, Denmark. Returning to the United States and the California Institute of Technology, Pauling was a full professor with 50 papers based on original research published by age 30. He became chairman of the Chemistry Department and director of Gates and Crellin Laboratories in 1931, and continued at the Institute until 1963. In 1939, Pauling published The Nature of the Chemical Bond and the structure of Molecules and Ciystals, which quickly became a classic in its field. His theories helped to explain complicated chemical bonds, such as the color in dyes. Many new drugs, plastics, and synthetic fibers were developed from his work. Researching proteins, Pauling and his associates produced synthetic antibodies by alter- mg molecules of globulins in the blood and developed a substitute for blood plasma from gelatin. Paul mg also studied the relationship between molecular abnormalities and hereditary diseases such as sickle cell anemia and mental retardation. Meanwhile, his outspoken antiwar position during the "McCarthy era" caused Pauling to be placed under suspicion as a Communist, a charge he strongly denied. However, his passport was restricted by the U.S. government until 1954, when he traveled freely to Stockholm, Sweden, to receive his first Nobel Prize
During the 1950's, Pauling was a leader of the campaign against nuclear testing. He spoke frequently about his concerns over the effects of radioactive fallout. In 1958, Pauling presented a petition to the United Nations, signed by 11,021 scientists from 49 countries, which called for an international ban on the testing of nuclear weapons. During the turbulent 1960's, Pauling was a vigorous voice in the antiwar movement In 1963, Pauling moved to the Center for the study of Democratic Institutions, then to the University of California at San Diego in 1967, and finally to Stanford University in 1969. Facing mandatory retirement at age 70, he established the Linus Pauling Institute of Science and Medicine. In 1970, he published Vitamin C and the Common Cold, advocating massive doses of vitamin C to provide immunity against infectious diseases. Pauling went on to suggest that vitamin C could also prevent cancer. Once again, Pauling had sparked a major controversy.

Teller, Edward (1908- ), an American physicist, became known as "the father of the hydrogen bomb." He was among the first to recognize the possibility of building the H-bomb and led the push for its development. Teller's many brilliant contributions to quantum mechanics and physical chemistry helped develop nuclear weapons and greatly advanced our understanding of the atom. As a child in Hungary, Teller showed an early brilliance in mathematics. As a young man, he was captivated by the emerging field of quantum mechanics, which combined theoretical and experimental physics. He received a Ph.D. in theoretical physics from the University of Leipzig, Germany (1930), and was immersed in research until the rise of the Nazis made work impossible for him. In 1934, Teller traveled to Copenhagen, Denmark, on a Rockefeller Foundation fellow-ship to study with Niels Bohr, one of the founders of modern physics. One year later, Teller left for the United States and a professorship at George Washington University. Dui mg this early part of his career, Teller's scientific papers greatly advanced the study of quantum mechanics and presented a theory C the molecule that remains the basis for scientific study today. As World War 11(1939-1945) began, physicists everywhere were becoming aware that an atom could be split and the creation of a terrible weapon was possible. In 1941, Teller was recruited to join the U.S. government's Manhattan Project in developing the first atomic bomb.
At Columbia University and the University of Chicago, he teamed up with Enrico Fermi, and at the laboratory in Los Alamos, New Mexico, he worked with J. Robert Oppenheimer. Teller was intensely involved in every step of the bomb's creation. Before the first atomic bomb was exploded, Teller provided reassuring calculations showing that an atomic blast would not set the oceans on fire and cause the entire world to burn. When the first atomic bomb - a fission explosion-was still in the works, Teller began pushing for development of a much more complicated and vastly more powerful fusion explosion-the hydrogen bomb. After the explosion of the fission bomb, Teller stood out among the scientists in his zeal for moving quickly to create this fusion H-bomb

In 1950, when the Soviet Union exploded its first atomic bomb and President Harry S. Truman approved development of a fusion bomb, Teller was already at work at Los Alamos. Two years later, the United States detonated the world's first hydrogen bomb. His theories proven, Teller returned to teaching and lobbying Washington for an ongoing build-up of nuclear arms. Teller was influential in the establishment of the Lawrence Livermore Laboratory in California, dedicated mainly to the design of nuclear weapons. He was associated with the laboratory and a professor of physics at the University of California until 1975. For decades, Teller remained a vigorous proponent of arms build-up, reacting to a perceived Soviet threat of war. He is the author of numerous books on nuclear war and on peaceful uses of nuclear energy. His many honors include the Enrico Fermi Award and the National Medal of Science.

Hodgkin, Dorothy Crowfoot

(1910 - 1994), a British chemist, won the 1964 Nobel Prize in chemistry for determining the highly complex structure of the vitamin B12 molecule. She also determined the molecular structure of cholesterol iodide, penicillin, insulin, and other organic compounds. Such studies are of practical importance in medicine. For example, expanded knowledge about the B12 molecule has led to better understanding of how the body uses this substance to build red blood cells. This knowledge has, in turn, led to successful treatment of a disease called pernicious anemia. Hodgkin used the technique of X-ray diffraction in her analysis of organic compound. X- ray diffraction is a valuable tool that has aided chemists in understanding the molecular structure of many substances, including DNA. This technique is based on diffraction properties of X rays. When the X rays are focused on a crystalline substance, the regular, repeating arrangement of molecules in the crystals diffracts, or bends, the X rays. The pal tern of the X-ray diffraction, which is also regular, can be studied. From these studies, chemists can determine the actual molecular structure of the crystals. Dorothy Hodgkin was born Dorothy Crow foot in Cairo, Egypt. She conducted most of her research at Oxford University. She was a member of the Royal Society.

Seaborg, Glenn Theodore

(1912- ), an American chemist, is best known for the discovery plutonium and a series of transuranium elements-radioactive elements which have atomic numbers heavier than 92, the atomic number of uranium. For his work in isolating plutonium, Seaborg, along with his colleague Edwin M. McMillan, received the Nobel Prize for chemistry in 1951. Seaborg was born in lshpeming, Michigan He received a B.A. from the University of California at Los Angeles (1934) and a Ph.D. degree from the University of California at Berkeley (1937). In the Berkeley chemistry laboratory in 1937, Seaborg and his colleagues began delving into the atomic structure of matter, isolating dozens of new isotopes for common elements. An isotope is one of two or more atoms of a chemical element with the same atomic number (number of protons in the nucleus), but a different atomic weight (number of neutrons in the nucleus).
In 1940, Seaborg gained the world's attention with his discovery of a new element plutonium, atomic number 94. Before Seaborg 5 discovery of plutonium and Edwin McMillan discovery of neptunium-atomic number 93-the periodic table of the elements, which lists all the known elements and their atomic numbers, was considered complete at uranium, the heaviest element. But, by bombarding uranium with nuclear particles, Seaborg and his staff were able to change the nucleus of uranium, an existing element, "transmuting" it into new, radioactive "transuranium" or "transuranic" elements. In 1941, as the United States entered World War II (1939-1945), Seaborg took a leave of absence from the University of California to continue his plutonium research at the metallurgical laboratory of the University of Chicago. There, he was part of the team building an atomic bomb. Seaborg's assignment was to create a chemical process for separating plutonium from uranium. He devised a method in just over one year, through ultra micro chemical research, using quantities a thousand times smaller than previously thought necessary for the task. By 1958, Seaborg had led in the discovery of a total of nine transuranium elements, with atomic numbers 94-102. Seaborg and his team also isolated a number of specific isotopes of these transuranium elements, the most famous being Plutonium 239. Plutonium 239 was found to readily undergo fission (splitting) when struck by neutrons, making it an ideal energy source for nuclear reactors or nuclear weapons. In 1946, Seaborg returned to California as a professor and director of nuclear chemical research at Berkeley, and was appointed to the General Advisory Committee of the U.S. Atomic Energy Commission. In 1958, Seaborg became chancellor of the University of California at Berkeley.

In 1961, President John F. Kennedy appointed Seaborg chairman of the U.S. Atomic Energy Commission, making him the first scientist to hold this vital post. Seaborg served as Kennedy's chief advisor on nuclear energy and met with Soviet officials to maintain the delicate nuclear weapons balance during the "Cold War." Seaborg returned to teach at Berkeley in 1971. He also served as director of the nuclear chemistry research laboratory at Berkeley until 1975.

Quarterman, Lioyd Albert

(1918-1982) was an African American nuclear chemist. As a member of the Manhattan Project team during World War 11(1939-1945), he helped create the first atomic bomb.
Born in Philadelphia, Quarterman graduated from St. Augustine's College, North Carolina in 1943 and received an M.S. degree from Northwestern University in 1952. From 1943 to 1946, Quarterman worked in a laboratory hidden underneath an unused football field at the University of Chicago. Here, he and the rest of the Manhattan Project team worked with famed nuclear scientist Enrico Fermi to develop the world's first nuclear reactor. This project was closed in 1946, and the Chicago research team became Argonne National Laboratories. Quarterman stayed with Argonne for about 30 years. This brilliant scientist is also known for his research in inorganic chemistry, particularly in forming fluoride compounds using Zeon, argon, and krypton. To study the molecular makeup of various elements, Quarterman devised a "diamond window." This cell "window," made of tiny diamonds capable of resisting corrosion by even the most caustic matter, enabled scientists to study solutions of such difficult-to-handle substances as hydrogen fluoride under an electromagnetic microscope.

Quarterman wrote many scientific articles and belonged to a number of prestigious societies. In addition to his professional duties, Quarterman often took time to visit Chicago public schools, where he encouraged African American students to pursue careers in science

Franklin, Rosalind Elsie

(1920-1958) was a British scientist who made important contributions to our understanding of complex organic molecules. Franklin used X-ray diffraction techniques to study crystal structures of molecules such as DNA. In X-ray diffraction, X rays are focused on a bit of material containing crystals of the substance to be studied. The atoms in crystals are arranged in planes, with regular spacing between each plane. When an X-ray beam travels through a crystal, the planes of atoms diffract, or spread apart, the rays into a regular pattern. Scientists can then study the diffraction patterns to learn more about the molecular structure of the substance. In 1951 Franklin began studying DNA crystals at the Biophysical Laboratory of King's College, London. Using X-ray diffraction studies, she discovered a number of important proper-ties of DNA. One of these properties is the helical structure of DNA, that is, its spiral shape. Another is the density of DNA. These discoveries helped James Watson and Francis Crick make an accurate model of the DNA molecule several years later. Building on her work with DNA, Franklin determined the structure of the tobacco mosaic virus. A virus is a complex molecule that has some characteristics of a living cell. In other X-ray diffraction research, Franklin analyzed structural changes in heated carbons. This work provided information that proved useful in the coking industry and in atomic technology.

Rosalind Elsie Franklin was born in London in 1920. She studied at Cambridge University, graduating in 1941. After graduation, Franklin worked for the British Coal Utilisation Research Association. In the late 1940's she studied X-ray diffraction techniques with Jacques Mering in Paris. In 1951 Franklin joined the Biophysical Laboratory at King's College, London. From 1953 to 1958 she worked in the Crystallography Laboratory at Birbeck College, London. Rosalind Franklin died in 1958 at the age of 37.

Sakharov, Andrei Dmitriyavich

(1921-1989) was the Soviet physicist most responsible for developing that nation's hydrogen bomb. He later became an internationally known social philosopher and an advocate for human right and world harmony. Harrison E. Salisbury's introduction to Sakharov's manifesto for world harmony, Progress, Coexistence, and Intellectual Freedom (1968), described Sakharov as an "Oppenheimer, Jeller, and Hans Bethe all rolled into one," who grew into a philosopher and social architect on a world scale. Graduating with honors from Moscow State University (1942), Sakharov showed intellectual talents so remarkable that he was exempted from military service to continue his studies during World War II (1939-1945). In 1945, he became an associate at the P. N. Le-bedev Physics Institute in Moscow, where he earned a Ph.D. in physical and mathematical sciences (1947). In the Soviet Union, this degree was generally reserved for more experienced scientists.
Between 1948 and 1956, Sakharov was engaged in secret research on nuclear weapons specifically directing development of the hydrogen bomb. In 1953, he became the youngest scientist ever to be elected to the prestigious Soviet Academy of Sciences. In the early 1960's, while he continued his research on the theoretical aspects of controlled fusion at the Lebedev Institute, Sakharov and his wife, Yelena Bonner, became outspoken critics of human rights violations in the Soviet Union and around the world. By the mid-1960's, Sakharov's research interest had changed from nuclear physics to the nature of the universe
In 1968, The New York Times printed Sakharov's Progress, Coexistence, and Intellectual Freedom. In this declaration, Sakharov laid out his plan for world peace and progress based on cooperation between the world's superpowers, with an emphasis on human rights and intellectual freedom. In 1970, Sakharov and two other physicists formed the Committee for Human Rights to give a stronger voice to their efforts to stop human rights violations within the Soviet Union. In 1975, Sakharov was awarded the Nobel Prize for Peace for his work in promoting world harmony and opposing violence

Reacting to his ceaseless criticism, the Soviet government arrested Sakharov in 1980, exiling him from Moscow to Gorki (now Nizhniy Novgorod, Russia), then an industrial center closed to foreigners. He was released in 1986 and returned to Moscow where he became part of a changed and changing government. In 1989, Sakharov was elected to the newly formed Soviet legislature, the Congress of People's Deputies. Sakharov's Memoirs, published in 1990 after his death, describe his life as a scientist and human rights advocate.

Bohr, Aage Niels (1922- ), Danish physicist and Nobel laureate, born in Copenhagen. The son of Niels Bohr, he assisted his father on the atomic bomb project at Los Alamos, New Mexico, during World War II. He then joined the Institute for Theoretical Physics in Copenhagen, devoting his attention to the inner structure of the atom.

In 1954 he wrote his doctoral thesis at the University of Copenhagen. It dealt with a collective motion theory of the atomic nucleus that he had developed with the United States physicist Ben R. Mottelson at the suggestion of the US physicist James Rainwater. The theory helped to explain many nuclear properties by showing that nuclear particles can vibrate and rotate so as to distort the shape of the nucleus from the expected spherical symmetry into an ellipsoid. Bohr, Mottelson, and Rainwater received the 1975 Nobel Prize for Physics for this work.

In 1963 Bohr became Director of the institute, now renamed in honour of his father. He resigned in 1970 to devote more time to research, but in 1975 he became Director of the Nordic Institute of Theoretical Atomic Physics, which shares research and facilities with the Niels Bohr Institute.

Lederman, Leon M. (1922- ), an American physicist, won the 1988 Nobel Prize for physics. He was honored for his groundbreaking contribution to our understanding of particle physics. Lederman shared the award with colleagues Melvin Schwartz and Jack Steinberger for research done by the three physicists in 1962. Their work enabled them to capture neutrinos and use them to discover other subatomic particles, including the muon neutrino believed to be one of the dozen building blocks of matter. Using a powerful nuclear accelerator at Brookhaven National Laboratory on Long Island, New York, the three physicists produce a beam of protons and directed it with an energy of 30 billion electron volts at a beryllium metal target When the protons slammed into the barrier, their atomic nuclei were shattered releasing new particles, including neutrinos. Particles were filtered out by a 44-foot thick steel barrier made from the plates of an old battleship. The barrier screened out all but the neutrinos, creating the first artificially produced neutrino beam. By artificially creating beams of neutrinos, Lederman and his associates made possible the study of the fundamental force that induces radioactive nuclear decay. Meanwhile, in studying the crash debris from the experiment, Lederman discovered a second type of neutrino, the muon. His findings showed that leptons-point like particles such as electrons and neutrons-react in pairs This work led to the development of the "standard model," considered the cornerstone of modern physics.
In 1977, Lederman led his research team in making another fundamental discovery. Working now with the Fermilab accelerator, Lederman and his associates found the upsilon particle, a new particle nine times heavier than the proton. This discovery offered the first evidence of a fifth and sixth quark (quarks are the still smaller entities of which protons and neutrons are believed to be composed).

Born to Russian parents who had immigrated to the United States, Lederman graduated from City College of New York in 1943, then served in the U.S. Signal Corps during World War 11(1939-1945). He received his PhD from Columbia University in 1951. He taught physics and continued his research there from 1952 to 1989. In 1979, Lederman also became director of Fermi National Accelerator Laboratory near Batavia, Illinois. Lederman remained at Fermilab, holding the top job in high-energy experimental physics, until he retired in 1989. In 1992, Lederman wrote The God Particle, an explanation of particle physics for the general public.

Zewail, Ahmed

Egyptian-American scientist won the Nobel Prize for chemistry today for demonstrating that a rapid laser technique can observe the motion of atoms in a molecule as they occur during a chemical reaction.
Ahmed Zewail was born in February 26, 1946, in Egypt where he grew up, Zewail received both his Bachelor of Science and his master's degrees from Alexandria University Alexandria. He began his professional career as an undergraduate trainee at Shell Corporation in Alexandria in 1966. After continued studies in the U.S.A. he graduated for Ph.D. in 1974 at the University of Pennsylvania. After the completion of his Ph.D., he went to the University of California, Berkeley, as an IBM research fellow. Zewail was appointed to the faculty at Caltech in 1976 at the age of 30 as an assistant professor of chemical physics. In 1982 he was tenured, as he became a full professor, and in 1990 was honored by the first Linus Pauling Chair at Caltech. At the age of 52, Zewail won the “Banjamin Franklin” prize after his latest scientific achievements known as the femto_second which is the smallest part of he second, he received the prize at a lavish ceremony attended by some 1,500 scientists, students, officials and figures, including former US Presidents Jimmy Carter and Gerald Ford. In 1999, Dr. Ahmed Zewail, a laser expert was nominated for the Nobel Prize for Chemistry and by that he is the first Egyptian to be nominated for this honourable prize. Dr. Zewail is the first originally Arab Muslim scientist to win such prize since Naguib Mahfouz, who won the literature prize in 1988, and late President Anwar Sadat, who shared the peace prize in 1978. But he is the first to take one of the prestigious awards for science. The Nobel carries an award of nearly one million dollars. Dr.Zewail currently holds both Egyptian and American Nationality. He has a family of four children and is married to Dema Zewail, a physician in public health (UCLA). His scientific family over the past 20 years consists of some 150 post-doctoral research fellows, graduate students and visiting associates. He lives in San Marino, California. Ahmed Zewail currently is the Linus Pauling Chair Professor of Chemistry and Professor of Physics at the California Institute of Technology, and Director of the NSF Laboratory for Molecular Sciences (LMS). Zewail's current research is devoted to developments of ultrafast lasers and electrons for studies of dynamics in chemistry and biology. In the field of femtochemistry, developed by the Caltech group, the focus is on the fundamental, femtosecond (10-15 second) processes in chemistry and in related fields of physics and biology.

Although we gave a brief useful summary about many scientists, there are others we didn't mention, others that helped in the progress of modern Chemistry, because if we did, that file you are reading will last forever ... We didn't ignore them, they'll never be forgotten ...