Dawn Holt, age 16, of Rockland, Ill., for her question:

WHAT IS XENON?

Xenon is a chemical element that makes up about one part in 20 million of the earth's atmosphere. It is obtained from liquid air. It is pronounced ZEN ON.

Two British chemists, Sir William Ramsay and Morris Travers, discovered xenon in 1898. Now the element is used in filling flash lamps and other powerful lamps. It is also used to make bubble chambers, instruments used in the study of nuclear particles.

Xenon is a tasteless, odorless, colorless gas. It is classed as an inert gas because it does not react readily with other substances.

Scientists once believed that xenon could not form chemical compounds but they now know that it can be compounded with fluorine and oxygen.