Earl Garvin, age 14, of Atlanta, Ga., for the question:

What is the halogen family?

The halogen brothers are chemical elements. Their family name means the salt makers. We find the halogens grouped together in the periodic atomic table. Each element, of course, has its own number of electrons Each halogen element has a different number of electrons. But each has seven electrons in its outer shell. Electrons try to arrange themselves in pairs, an odd number electron is always eager to find a partner. This can be done by teaming up with another atom which also needs one more electron to make a pair.

Then this happens, the teamed atoms form a compound, something entirely different from the two basic elements. The halogens with their outer shells of seven atoms are always eager to go into partnership. They team up with many other elements and form a long, long list of compounds. Halogen compounds do everyday work in the kitchen, the public water supply, the operating rooms the camera, the dye works ‑ to name a few.

There are four busy halogen brothers in everyday use. The first is fluorine, whose name means to flow. This busy element is a pale yellow gas, active enough to eat its way through glass. It combines with calcium to form fluorspar, a flux used to purify iron. Hydrofluoric acid is used to etch the degree marks on thermometers.

The best known halogen in our everyday lives is chlorine, whose name means the yellow one. Chlorine is a heavy yellow gas, always eager to react with water. In so doing, it frees oxygen from the water and these freed oxygen atoms are very active. They attack bacteria and bleach out dyes. These hydrochlorous acid compounds are used to purify our reservoirs.

Chlorine also combines with lye to form sodium hypochloritc. This is the strong smelling cleaner‑upper we use to clean the sink and kill the germs in the drainpipe. Before the days of wonder drugs, sodium hypochlorite was used to sterilize fagged wounds.

Chlorine also combines with lime. This forms calcium hypochlorite, a powerful bleaching material. Chlorate compounds are formed at high temperatures. Sodium chlorate is a wend killer, death to the pesky Canadian thistle. Potassium chlorate has a very low kindling point and is used to make match heads. Chlorine combines with methane to form chloroform and carbon tetrachloride, a cleaning fluid and a fire extinguisher.

Bromine is another halogen, whose name refers to its horrible smell. It is present in the ethyl used to refine gasoline. Sodium bromide is a nerve medicine arid silver bromide is the compound used on photographic film.

The fourth halogen in everyday use is iodine, the violet one, kit ordinary temperature it forms steal grey crystals. When hot, it becomes a beautiful violet gas. Mixed with alcohol it becomes a brown liquid. You know what that is for.

There is a fifth halogen, but it is unstable and known only in the laboratory. The four everyday halogens are rarely seen in pure form. But we use the compounds they form every day of our lives.