Chemicals/Xenons

Xenon, a heavy chemical element with the symbol Xe and atomic number 54, is a colorless, dense, odorless noble gas found in Earth's atmosphere in trace amounts.

Emissions
Xenon is a trace gas in Earth's atmosphere, occurring at $87 nL/L$ (parts per billion), or approximately 1 part per 11.5 million.

Gases
The first excimer laser design used a xenon dimer molecule (Xe2) as the lasing medium energized by a beam of electrons to produce stimulated emission at an ultraviolet wavelength of 176 nm.

Liquids
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.

Solids
Under the same conditions, the density of solid xenon, 3.640 g/cm3, is greater than the average density of granite, 2.75 g/cm3. Under gigapascals of pressure, xenon forms a metallic phase.

Solid xenon changes from (fcc) to (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 appears 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 width of the electron bands in that state.

Isotopes
Naturally occurring xenon consists of seven stable isotopes and two long-lived radioactive 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. Radioactive xenon-135 is produced by beta decay from iodine-135 (a product of nuclear fission), and is the most significant (and unwanted) neutron absorber in nuclear reactors.

Solar systems
Within the Solar System, the nucleon fraction of xenon is 1.56 × 10−8, for an abundance of approximately one part in 630 thousand of the total mass. Xenon is relatively rare in the Sun's atmosphere, on Earth, and in asteroids and comets. The abundance of xenon in the atmosphere of planet Jupiter is unusually high, about 2.6 times that of the Sun. Mass fraction calculated from the average mass of an atom in the solar system of about 1.29 atomic mass units. This abundance remains unexplained, but may have been caused by an early and rapid buildup of planetesimals—small, subplanetary bodies—before the heating of the presolar disk. (Otherwise, xenon would not have been trapped in the planetesimal ices.) The problem of the low terrestrial xenon may be explained by covalent bonding of xenon to oxygen within quartz, reducing the outgassing of xenon into the atmosphere.

Stars
Unlike the lower-mass noble gases, the normal stellar nucleosynthesis process inside a star does not form xenon. Elements more massive than iron-56 consume energy through fusion, and the synthesis of xenon represents no energy gain for a star. Instead, xenon is formed during supernova explosions, in classical nova explosions, by the slow neutron-capture process (s-process) in red giant stars that have exhausted their core hydrogen and entered the asymptotic giant branch, and from radioactive decay, for example by beta decay of extinct iodine-129 and spontaneous fission of thorium, uranium, and plutonium.

Resources

 * Chemicals/Actinides
 * Chemicals/Aluminums
 * Chemicals/Berylliums
 * Chemicals/Leads
 * Chemicals/Lithiums
 * Chemicals/Nickels
 * Chemicals/Sulfurs
 * Chemicals/Thoriums