How would you classify oxygen? It is present in gas form, a component of air, but does not conduct electricity. Oxygen is not metallic, in fact unless subjected to high pressures, it is colorless! Oxygen also tends to gain electrons in compounds. Scientists have a name for oxygen and other elements like it. The classification of these elements is nonmetals.
Nitrogen is a major component of air. It makes up eighty percent of air on Earth. The nitrogen gas molecule(N2) is made up of a strong triple bond, therefore it is not very reactive in this state. However, nitrogen is essential to life. To use nitrogen, plants (and the animals that eat the plants) reley on nitrogen-fixing bacteria in the soil to break the strong triple bonds of N2 in atmosphere. It is then nitrogen can form compounds that can used for a variety of purposes.
Phosphorus is also part of the nitrogen family. As a nonmetal, it tends to form various allotropes. Their are three common allotropes of phosphorus. They are white phosphorus, black phosphorus, and red phosphorus.
White phosphorus has molecules of the form P4. The molecular structure resembles a tetrahedral pyrimid. It very reactive in air; it can ignite in air at temperature as low as thirty degrees celicius. When white phosphorus and oxygen are combined at room temperature, energy in the form of blue-green light is given off.
Black phosphorus can be obtained by subjecting white phosphorus to high temperatures. Black phosphorus is less reactive that white phosphorus. It consists of a network of phosphorus atoms with each atom attached to three others ultimately forming a double layer structure.
Red phosphorus consists of P4 bonded in a random structure. Black and red phosphorus have higher melting and boiling points that white phosphorus. Red phosphorus will ignite in air at 260 degrees celicius. It is used in the striking surface of a box of matches.
Phosphorus is not found in it pure state in nature. It can be found in the mineral apatite, 3Ca3(PO4)2 * CaF2.
Oxygen is present in air, and can form a compound with almost every other element. It is present in many vital compounds, including water. Oxygen is used in cellur respiration and in is necessary in the combustion of hydrocarbons. O>sub>2 is known to be the most stable form of the element. It is a diatomic moleculcule. However, oxygen has a infamous allotrope. O3, or ozone is a dangerous form of oxygen. It is produce by a strong electrical discharge with oxygen. Lighting, or an electric motor may produce enough energy to cause such a change. Ozone has been known to break down many compounds. The conversion of many O2 molecules in the air to ozone can result from a chain reaction caused by a free oxygen atom. This can lead to a decrease in oxygen in the atmosphere, thereby hampering life processes that depend on oxygen.
Sulfur can existis in many allotropic forms at different temperatures. Its most common allotropic form is a ring of eight sulfur atoms joined together. At temperatures higher than 165 degree Celcius, sulfur joins into a chainlike molecule to form several other allotropes. By boiling sulfur, and immediately cooling it, a rubbery material consisting of sulfur will be formed. The stable allotropic form of sulfur (S8), which is a yellow powdery substance with an odor, can be obtain by cooling other allotropes of sulfur to room temperature.
The elements that make up the halogen familoy are reactive nonmetals. They tend to gain an electron in a compound and form diatomic molecules among themselves (e.g. F2, I2, Cl2). Diatomic molecules have nonpolar, convalent bonds between the elements they consist of. As you move down the family, starting with fluorine, each element can replace the element below it. For example, chlorine can replace iodine in a reaction, but it cannot replace flourine. In fact, flourine cannot be replace by any other halogens since it is the most active member of the group. It is also known that flourine can not be replace any element in the perodic table. Astatine (At) is any extremely rare memeber of the group. Not a great deal of reaction takes place with astatine in the laboratory.
Each halogen also has a distinctive color and odor. Flourine is pale yellow, chlorine is yellow-green, bromine is dark orange, iodine is violet, and astatine is an unstable compound.
Noble gases are generally inert gases. An inert material will not react with another material. Thus the name noble gases are given to this family. They do not associate with other elements. Therefore the formula for the noble gases is as follows: He (helium), Ne (neon), Ar (argon), Kr (krypton), Xe (xenon), and Rn (radon). A few compounds under very, very special conditions have been produce with xenon and krypton, but none with helium, argon, or neon. Helium is used to inflate objects. Argon and krypton are used in light bulbs to provide an atmosphere that could keep the filament from wearing out; the gases do not react with the filament. Noble gases are also used to produce brilliant colors in flourescent bulbs and light signs. Electricity in the bulbs and signs exite the electrons, thus causing them to emit energy in the form of light.
|Table of Contents:
Unit 4 - Section 3