Xenon is a chemical element with symbol Xe and atomic number 54. It is a colorless, dense, odorless noble gas found in the Earth’s atmosphere in trace amounts. Although generally unreactive, xenon can undergo a few chemical reactions such as the formation of xenon hexafluoroplatinate, the first noble gas compound to be synthesized.
Naturally occurring xenon consists of eight stable isotopes. More than 40 unstable xenon isotopes undergo radioactive decay, and the isotope ratios of xenon are an important tool for studying the early history of the Solar System.
Xenon is used in flash lamps and arc lamps, and as a general anesthetic. The first excimer laser design used a xenon dimer molecule (Xe2) as the lasing medium, and the earliest laser designs used xenon flash lamps as pumps. Xenon is used to search for hypothetical weakly interacting massive particles and as the propellant for ion thrusters in spacecraft. Its relative scarcity has limited wide spread use
Xenon is an inert gas and does not (easily) form compounds, nor does it ionize in water.