Brian Nichols, age 15, of Twin Falls, Ids., for his question:

WHAT ARE NOBLE GASES?

Noble gases are a group of six gaseous chemical elements. They are also called inert gases. In order of increasing  atomic weight, they are helium, neon, argon, krypton, xenon and radon.

For many years chemists believed that these gases, because their outermost shells were completely filled with electrons,  were inert    that is, that they would not enter into chemical combinations with other elements or compounds. This is now known not to be true, at least for the three heaviest inert gases: krypton, xenon and radon.

Liquefied noble gases under pressure, particularly xenon, are employed as solvents in infrared spectroscopy. They are used for this because they are transparent to infrared radiation and therefore do not obscure the spectra of the dissolved substances.

Compounds of helium, neon or argon, the electrons of which are more closely bound to their nuclei than are krypton, xenon and radon, are unlikely to be created.