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The Atom2
Sub-Nucleonic Particles (Quarks):
Nucleons are neutrons or protons. Thus,
sub-nucleonic particles are smaller than and compose nucleons. These
particles are called quarks.
There are six types of quarks: up, down, strange, charm, truth, and beauty. (The scientists who discovered quarks got a little creative with their naming scheme..)
The proton is composed of two up quarks and one down quark bound together.
The neutron is composed of one up quark and two down quarks. By adding the
charges of individual quarks together, we can show the charges of the nucleons
they compose. Consider the following chart:
A proton is composed of uud (up-up-down), and a neutron is made up of udd
(up-down-down).
Proton's charge = charges of its components added = 2/3 + 2/3 + -1/3 = 1
Quarks can compose particles other than protons or neutrons. However, these
particles are very exotic and rare. They also usually have very short lives;
they often decay after less than a second. Single quarks have never been
observed, and it is believed that quarks must exist in pairs or triplets.
Quarks are thought to be fundamental particles, which means that nothing
smaller composes them. This is not proven, however. It is possible that
quarks are also composed of smaller particles.
Einstein's Equation, E = mc2:What does this famous and mysterious equation mean? We've all seen it, and yet a lot of us don't understand it or its implications. Essentially, it states:Energy = mass x c2. ; c is the speed of light. This is an incredibly large number because light travels extremely quickly. Think about it: When you flick a light switch, light appears instantaneously. This is because light travels so fast from the light source to you that it seems to take no time at all. The actual speed of light is about 300,000 kilometers a second (186,000 miles/second). If you were in an airplane that traveled at the speed of light, you could completely circle the earth in less than a second. That's FAST!! Now that we know what the equation means literally, what are its implications? Basically, it shows that energy is matter, and that they are interchangeable. Matter can be turned into energy, and energy can be turned into matter. This means that if a particle gains a lot of energy, it appears to have gained mass, because energy is mass. Thus, a particle's mass depends on its environment. If its environment is very hot (and thus has a lot of energy), it can gain mass in the form of gained energy. Additionally, if even a small amount of mass is converted to energy, a gargantuan amount of energy is still released. This is because the speed of light is so large a number. For instance, we can determine the amount of energy that composes one kilogram of mass by plugging the numbers into the equation using the speed of light in meters/second. The energy is measured in joules, which is the standard energy unit in the metric system.
Energy = 1 kg x (the speed of light in meters/second)2
This is equivalent to 25,000,000,000 kWh (kiloWatt hours) of electricity, or 25 billion kWh. This is enough electricity to power 47,564,688 60-watt light bulbs for an entire year. Thus, it is quite easy to see that just one kilogram of matter is equivalent to an enormous amount of energy. However, it turns out that there is no practical way to convert mass completely into energy. At least, not yet.
Anti-Matter:You may have watched the American TV show, "Star Trek". They talk occasionally about anti-matter as the source of power for the ship. Well, it turns out that anti-matter isn't just science fiction. Anti-matter is actually science fact. But, what is it? Simply put, anti-matter is the opposite of normal matter. For every "normal" particle of matter there is an opposite, anti-particle. There are anti-electrons, which are just like electrons but, instead of a negative charge, carry a positive charge. They are called positrons. There are anti-protons and anti-neutrons, which are composed of anti-quarks that are just like real quarks, but have opposite properties. Anti-protons are negatively charged instead of being positively charged. Anti-neutrons are neutral, just like normal neutrons, but have the opposite spin of a regular neutron. (Spin is another property of particles) There are even anti-atoms. These atoms are composed of anti-neutrons, anti-protons, and positrons (anti-electrons). So, you might be wondering, "Have I ever seen anti-matter?". The answer is no, and here's a tip: If you do see a lump of antimatter moving towards, you.... run. Whenever anti-matter comes in contact with matter, both masses convert directly into energy in a violent explosion. Anti-particles don't last long on earth because they almost instantly annihilate themselves on matter particles. However, their presence has been recorded in specially designed machines whose purpose is to create anti-matter, among other things. Antimatter-matter annihilation is the only way known for atoms to completely convert to energy. It could be a possible energy source in the future. If a 1/2 kilogram of anti-matter could be created and stored, it could be combined with a 1/2 kilogram of regular matter to release the amount of energy equivalent to 1 kilogram, which is what we described in the above section. However, as of now, no one knows how to make that much antimatter, and, if we could, no one knows how to store it safely. We'll leave those problems to Star Trek and the Starship Enterprise for now.
Masses of the Nucleons:We have a confession to make. We lied to you (again). In our explanation of Atomic Nomenclature, we implied that neutrons and protons have the same mass. This is not true. The neutron is actually .16% bigger than the proton. This is a result of the fact that neutrons and protons are made of different quarks. The neutron is u-d-d, while the proton is u-u-d. The up quark has a very slight difference in mass from the down quark, and this results in the discrepancy between the masses of the neutron and proton. This discrepancy is really not that big, and thus is not incredibly important when figuring the mass of an atom. It is also important to remember that the mass of a neutron and a proton can also change with an increase or decrease in energy of the particle. Energy is mass, after all. Additionally, the individual nucleons in an atom give up some of their mass to hold the atom together. This mass that is "given up" is present in the form of energy in the nucleus. Because it binds the atom together, it is called "binding energy". The mass each nucleon gives up is also relatively small.
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