Krypton is an element denoted by the atomic symbol Kr. Its atomic number is 36 and its atomic weight is 83.80. In its natural form it is a colorless, odorless, tasteless gas. It is found in the atmosphere in small quantities (about one part per million), and trace amounts occur in minerals, mineral springs, and meteorites. Commercially, krypton is produced by separation from liquefied air. The gas has some 26 isotopes, of which about 20 are radioactive. Nuclear reactors produce radioactive krypton isotopes as by-products of power generation. These isotopes can also be created by nuclear particle accelerators.

When the first Superman comic book appeared in 1938, the word "krypton" entered the American vocabulary as the planet where the hero was born and "kryptonite" as the mysterious substance that could rob him of his powers. While the planet and the mineral are fiction, their namesake exists as an inert gas. The story of...