Argon

Argon, AHR gon, is a chemical element that forms 0.94 percent of Earth's atmosphere. Most... More >>

Chlorine

Chlorine, KLAWR een, is a poisonous, yellowish-green gas with a strong, unpleasant odor. Chlorine... More >>

Fluorine

Fluorine, FLOO uh reen, is a chemical element. At ordinary temperatures, it is a pale yellow gas.... More >>

Hydrogen

Hydrogen (chemical symbol, H) is the simplest atom and the most abundant chemical element. The... More >>

Krypton

Krypton, KRIHP ton, is a chemical element that makes up only about one-millionth of Earth's... More >>

Noble gas

Noble gas refers to any of a group of six chemical elements. These elements are argon (Ar),... More >>

Oxygen

Oxygen is a life-supporting gas and a chemical element. Nearly all living things need oxygen to... More >>

Xenon

Xenon, ZEE non or ZEHN on, is a chemical element that makes up about 1 part in 20 million of... More >>