Unit 4: Up Close: The Periodic Table of Elements

Section 4: Representative Nonmetals

* Introduction
* The Nitrogen Family
* The Oxygen Family
* The Halogens
* Noble Gases

Introduction

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.

The Nitrogen Family

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.

The Oxygen Family

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. O2 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 Halogens

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

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.