Xenon - Periodic Table of Videos

Xenon is a chemical element with symbol Xe and atomic number 54. It is a colorless, dense, odorless noble gas, that occurs in the Earth's atmosphere in trace amounts.^[10] 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.^[11][12][13]
Xenon is used in flash lamps^[14] and arc lamps,^[15] and as a general anesthetic.^[16] The first excimer laser design used a xenon dimer molecule (Xe₂) as its lasing medium,^[17] and the earliest laser designs used xenon flash lamps as pumps.^[18] Xenon is also being used to search for hypothetical weakly interacting massive particles^[19] and as the propellant for ion thrusters in spacecraft.^[20]
Naturally occurring xenon consists of eight stable isotopes. There are also over 40 unstable isotopes that undergo radioactive decay. The isotope ratios of xenon are an important tool for studying the early history of the Solar System.^[21] Radioactive xenon-135 is produced by beta decay from iodine-135 (which is a product of nuclear fission), and it acts as the most significant neutron absorber in nuclear reactors.^[22]
Xenon has atomic number 54; that is, its nucleus contains 54 protons. At standard temperature and pressure, pure xenon gas has a density of 5.761 kg/m³, about 4.5 times the surface density of the Earth's atmosphere, 1.217 kg/m³.^[45] As a liquid, xenon has a density of up to 3.100 g/mL, with the density maximum occurring at the triple point.^[46] Notably, liquid xenon has a high polarizability due to its large atomic volume, and thus is an excellent solvent. It can dissolve hydrocarbons, biological molecules, and even water.^[47] Under the same conditions, the density of solid xenon, 3.640 g/cm³, is higher than the average density of granite, 2.75 g/cm³.^[46] Using gigapascals of pressure, xenon has been forced into a metallic phase.^[48]
Solid xenon changes from face-centered cubic (fcc) to hexagonal close packed (hcp) crystal phase under pressure and begins to turn metallic at about 140 GPa, with no noticeable volume change in the hcp phase. It is completely metallic at 155 GPa. When metallized, xenon looks sky blue because it absorbs red light and transmits other visible frequencies. Such behavior is unusual for a metal and is explained by the relatively small widths of the electron bands in metallic xenon.^[49][50]