: a colorless relatively inert gaseous element found in air at about one part per million—symbol Kr; see element table
Chemical element, chemical symbol Kr, atomic number 36. One of the noble gases, it is colourless, odourless, tasteless, and almost totally inert, combining only with fluorine under very rigourous conditions. Krypton occurs in trace amounts in the atmosphere and in rocks and is obtained by fractional distillation of liquefied air. It is used in luminescent tubes, flash lamps, incandescent light bulbs, lasers, and tracer studies.