xenon , Chemical element, chemical symbol Xe, atomic number 54. One of the noble gases, it is colourless, odourless, tasteless, and nearly inert, combining only with fluorine and oxygen and in complexes (see bonding). Xenon occurs in slight traces in Earth’s atmosphere and in rocks. Obtained by fractional distillation of liquefied air, it is used in luminescent tubes (see electric discharge lamp), flash lamps, lasers, and tracer studies and as an anesthetic.