Xenon

=**Xenon:**=

Xenon was discovered in 1898 by William Ramsay and Morris Travers. They discovered it in the residue remaining after liquid air had been fractionally distilled. Spectroscopic analysis showed the previously unseen beautiful blue lines that indicated the presence of a new element - xenon. Travers wrote of their discovery, "krypton yellow appeared very faint, the green almost absent. Several red lines, three brilliant and equidistant, and several blue lines were seen. Is this pure krypton, at a pressure which does not bring out the yellow and green, or a new gas? Probably the latter!" Although xenon is rare and relatively expensive to extract from the Earth's atmosphere it has a number of __applications__.

Can be used to image the heart, lungs and brain through gamma emmisson of this.

The name comes from the Greek word 'xenos', "Meaning stranger".
Harmful effects: Xenon is not considered to be toxic but many of its compounds are toxic as a result of their strong oxidizing properties.

Characteristics: Xenon is a rare, colorless, odorless heavy gas.

Xenon is inert towards most chemicals.

Many compounds of xenon have now been made, principally with fluorine or oxygen. Both oxides, xenon trioxide (XeO3) and xenon tetroxide (XeO4) are highly explosive.

Uses of Xenon Xenon is used in photographic flashes, in high pressure __arc lamps__ for motion picture projection, and in high pressure arc lamps to produce ultraviolet light.
 * used in making electron tubes, stroboscopic lamps, bactericidal lamps, and lamps used to excite ruby lasers for generating coherent light
 * used in the atomic energy field in bubble chambers, probes, and other __applications__ where its high molecular __weight__ is of value
 * potentially useful as a gas for ion engines
 * the perxenates are used in analytical chemistry as oxidizing agents

It is used in instruments for radiation detection, e.g., neutron and X-ray counters and bubble chambers.

Xenon is used in medicine as a general anaesthetic and in __medical__ imaging.

Modern ion thrusters for space travel use inert gases - especially xenon - for propellant, so there is no risk of the explosions associated with chemical propulsion.

An example in which xenon can be found in is mainly in the Earth's atmosphere, but also it can be found as a general anesthetic. In the Earth's crust there are 30 parts per trillion by weight, or 5 parts per trillion by moles. Xenon is a trace gas in the Earth's atmosphere. it is obtained commercially by fractional distillation of liquid air. Xenon has a Covalent Radius of 131.


 * Medical Uses:**

Anesthesia
Xenon has been used as a general anesthetic. Although it is expensive, anesthesia machines that can deliver xenon are about to appear on the European __market__, because advances in recovery and recycling of xenon have made it economically viable. Two physiological mechanisms for xenon anesthesia have been proposed. The first one involves the inhibition of the calcium ATPase pump—the mechanism cells use to remove calcium (Ca2+)—in the __cell__ membrane of synapses. This results from a conformational change when xenon binds to nonpolar sites inside the protein. The second mechanism focuses on the non-specific interactions between the anesthetic and the lipid membrane. Xenon has a minimum alveolar concentration (MAC) of 72% at age 40, making it 44% more potent than N2O as an anesthetic. Thus it can be used in concentrations with oxygen that have a lower risk of hypoxia. Unlike nitrous oxide (N2O), xenon is not a greenhouse gas and so it is also viewed as environmentally friendly. Xenon vented into the atmosphere is being returned to its original source, so no environmental impact is likely.

Imaging
Gamma emission from the radioisotope Xe of xenon can be used to image the heart, lungs, and brain, for example, by means of single photon emission computed tomography. 133Xe has also been used to measure blood flow. Xenon, particularly hyperpolarized Xe, is a useful contrast agent for magnetic resonance imaging (MRI). In the gas phase, it can be used to image empty space such as cavities in a porous sample or alveoli in lungs. Hyperpolarization renders Xe much more detectable via magnetic resonance imaging and has been used for studies of the lungs and other tissues. It can be used, for example, to trace the flow of gases within the lungs. Because xenon is soluble in water and also in hydrophobic solvents, it can be used to image various soft living tissues.

Many oxygen-containing xenon compounds are toxic due to their strong oxidative properties, and explosive due to their tendency to break down into elemental xenon plus diatomic oxygen (O2), which contains much stronger chemical bonds than the xenon compounds. Xenon gas can be safely kept in normal sealed glass or metal containers at standard temperature and pressure. However, it readily dissolves in most plastics and rubber, and will gradually escape from a container sealed with such materials. Xenon is non- toxic, although it does dissolve in blood and belongs to a select group of substances that penetrate the blood-brain barrier , causing mild to full surgical anesthesia when inhaled in high concentrations with oxygen.
 * Possible Dangers:**

Characteristics
[|Xenon flash] 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. [|[40]] As a liquid, xenon has a density of up to 3.100 g/mL, with the density maximum occurring at the triple point. [|[41]] 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. [|[41]] Using [|gigapascals] of [|pressure], xenon has been forced into a metallic phase. [|[42]] 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 metalized, 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. [|[43]] [|[44]] Xenon is a member of the zero- [|valence] elements that are called [|noble] or [|inert] [|gases]. It is inert to most common chemical reactions (such as combustion, for example) because the outer [|valence shell] contains eight electrons. This produces a stable, minimum energy configuration in which the outer electrons are tightly bound. [|[45]] However, xenon can be [|oxidized] by powerful oxidizing agents, and many xenon compounds have been synthesized. In a [|gas-filled tube], xenon emits a [|blue] or [|lavenderish] glow when the gas is excited by [|electrical discharge]. Xenon emits a band of [|emission lines] that span the visual spectrum, [|[46]] but the most intense lines occur in the region of blue light, which produces the coloration. [|[47]] ↑ ↓ [|Rn] ||  ||   ||    ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||   ||    || ** 54 Xe ** [|Periodic table] Spectral lines of xenon || or  [|/] [|ˈ] [|z] [|iː] [|n] [|ɒ] [|n] [|/] [|//**zee**-non//] [|[2]] || 5.894 g/L || (rarely more than 0) (weakly [|acidic] oxide) || ||
 * ||= [|Kr]
 * Xe**
 * [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 3: Lithium (Li), Alkali metal" link="http://en.wikipedia.org/wiki/Lithium"]] ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 4: Beryllium (Be), Alkaline earth metal" link="http://en.wikipedia.org/wiki/Beryllium"]]  ||||||||||||||||||||||||||||||||||||||||||||||||   ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 5: Boron (B), Metalloid" link="http://en.wikipedia.org/wiki/Boron"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 6: Carbon (C), Other non-metal" link="http://en.wikipedia.org/wiki/Carbon"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 7: Nitrogen (N), Other non-metal" link="http://en.wikipedia.org/wiki/Nitrogen"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 8: Oxygen (O), Other non-metal" link="http://en.wikipedia.org/wiki/Oxygen"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 9: Fluorine (F), Halogen" link="http://en.wikipedia.org/wiki/Fluorine"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 10: Neon (Ne), Noble gas" link="http://en.wikipedia.org/wiki/Neon"]]  ||
 * [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 11: Sodium (Na), Alkali metal" link="http://en.wikipedia.org/wiki/Sodium"]] ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 12: Magnesium (Mg), Alkaline earth metal" link="http://en.wikipedia.org/wiki/Magnesium"]]  ||||||||||||||||||||||||||||||||||||||||||||||||   ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 13: Aluminium (Al), Other metal" link="http://en.wikipedia.org/wiki/Aluminium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 14: Silicon (Si), Metalloid" link="http://en.wikipedia.org/wiki/Silicon"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 15: Phosphorus (P), Other non-metal" link="http://en.wikipedia.org/wiki/Phosphorus"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 16: Sulfur (S), Other non-metal" link="http://en.wikipedia.org/wiki/Sulfur"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 17: Chlorine (Cl), Halogen" link="http://en.wikipedia.org/wiki/Chlorine"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 18: Argon (Ar), Noble gas" link="http://en.wikipedia.org/wiki/Argon"]]  ||
 * [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 19: Potassium (K), Alkali metal" link="http://en.wikipedia.org/wiki/Potassium"]] ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 20: Calcium (Ca), Alkaline earth metal" link="http://en.wikipedia.org/wiki/Calcium"]]  ||||||||||||||||||||||||||||   ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 21: Scandium (Sc), Transition metal" link="http://en.wikipedia.org/wiki/Scandium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 22: Titanium (Ti), Transition metal" link="http://en.wikipedia.org/wiki/Titanium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 23: Vanadium (V), Transition metal" link="http://en.wikipedia.org/wiki/Vanadium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 24: Chromium (Cr), Transition metal" link="http://en.wikipedia.org/wiki/Chromium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 25: Manganese (Mn), Transition metal" link="http://en.wikipedia.org/wiki/Manganese"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 26: Iron (Fe), Transition metal" link="http://en.wikipedia.org/wiki/Iron"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 27: Cobalt (Co), Transition metal" link="http://en.wikipedia.org/wiki/Cobalt"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 28: Nickel (Ni), Transition metal" link="http://en.wikipedia.org/wiki/Nickel"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 29: Copper (Cu), Transition metal" link="http://en.wikipedia.org/wiki/Copper"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 30: Zinc (Zn), Transition metal" link="http://en.wikipedia.org/wiki/Zinc"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 31: Gallium (Ga), Other metal" link="http://en.wikipedia.org/wiki/Gallium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 32: Germanium (Ge), Metalloid" link="http://en.wikipedia.org/wiki/Germanium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 33: Arsenic (As), Metalloid" link="http://en.wikipedia.org/wiki/Arsenic"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 34: Selenium (Se), Other non-metal" link="http://en.wikipedia.org/wiki/Selenium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 35: Bromine (Br), Halogen" link="http://en.wikipedia.org/wiki/Bromine"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 36: Krypton (Kr), Noble gas" link="http://en.wikipedia.org/wiki/Krypton"]]  ||
 * [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 37: Rubidium (Rb), Alkali metal" link="http://en.wikipedia.org/wiki/Rubidium"]] ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 38: Strontium (Sr), Alkaline earth metal" link="http://en.wikipedia.org/wiki/Strontium"]]  ||||||||||||||||||||||||||||   ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 39: Yttrium (Y), Transition metal" link="http://en.wikipedia.org/wiki/Yttrium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 40: Zirconium (Zr), Transition metal" link="http://en.wikipedia.org/wiki/Zirconium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 41: Niobium (Nb), Transition metal" link="http://en.wikipedia.org/wiki/Niobium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 42: Molybdenum (Mo), Transition metal" link="http://en.wikipedia.org/wiki/Molybdenum"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 43: Technetium (Tc), Transition metal" link="http://en.wikipedia.org/wiki/Technetium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 44: Ruthenium (Ru), Transition metal" link="http://en.wikipedia.org/wiki/Ruthenium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 45: Rhodium (Rh), Transition metal" link="http://en.wikipedia.org/wiki/Rhodium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 46: Palladium (Pd), Transition metal" link="http://en.wikipedia.org/wiki/Palladium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 47: Silver (Ag), Transition metal" link="http://en.wikipedia.org/wiki/Silver"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 48: Cadmium (Cd), Transition metal" link="http://en.wikipedia.org/wiki/Cadmium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 49: Indium (In), Other metal" link="http://en.wikipedia.org/wiki/Indium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 50: Tin (Sn), Other metal" link="http://en.wikipedia.org/wiki/Tin"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 51: Antimony (Sb), Metalloid" link="http://en.wikipedia.org/wiki/Antimony"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 52: Tellurium (Te), Metalloid" link="http://en.wikipedia.org/wiki/Tellurium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 53: Iodine (I), Halogen" link="http://en.wikipedia.org/wiki/Iodine"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 54: Xenon (Xe), Noble gas" link="http://en.wikipedia.org/wiki/Xenon"]]  ||
 * [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 55: Caesium (Cs), Alkali metal" link="http://en.wikipedia.org/wiki/Caesium"]] ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 56: Barium (Ba), Alkaline earth metal" link="http://en.wikipedia.org/wiki/Barium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 57: Lanthanum (La), Lanthanoid" link="http://en.wikipedia.org/wiki/Lanthanum"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 58: Cerium (Ce), Lanthanoid" link="http://en.wikipedia.org/wiki/Cerium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 59: Praseodymium (Pr), Lanthanoid" link="http://en.wikipedia.org/wiki/Praseodymium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 60: Neodymium (Nd), Lanthanoid" link="http://en.wikipedia.org/wiki/Neodymium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 61: Promethium (Pm), Lanthanoid" link="http://en.wikipedia.org/wiki/Promethium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 62: Samarium (Sm), Lanthanoid" link="http://en.wikipedia.org/wiki/Samarium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 63: Europium (Eu), Lanthanoid" link="http://en.wikipedia.org/wiki/Europium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 64: Gadolinium (Gd), Lanthanoid" link="http://en.wikipedia.org/wiki/Gadolinium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 65: Terbium (Tb), Lanthanoid" link="http://en.wikipedia.org/wiki/Terbium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 66: Dysprosium (Dy), Lanthanoid" link="http://en.wikipedia.org/wiki/Dysprosium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 67: Holmium (Ho), Lanthanoid" link="http://en.wikipedia.org/wiki/Holmium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 68: Erbium (Er), Lanthanoid" link="http://en.wikipedia.org/wiki/Erbium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 69: Thulium (Tm), Lanthanoid" link="http://en.wikipedia.org/wiki/Thulium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 70: Ytterbium (Yb), Lanthanoid" link="http://en.wikipedia.org/wiki/Ytterbium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 71: Lutetium (Lu), Lanthanoid" link="http://en.wikipedia.org/wiki/Lutetium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 72: Hafnium (Hf), Transition metal" link="http://en.wikipedia.org/wiki/Hafnium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 73: Tantalum (Ta), Transition metal" link="http://en.wikipedia.org/wiki/Tantalum"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 74: Tungsten (W), Transition metal" link="http://en.wikipedia.org/wiki/Tungsten"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 75: Rhenium (Re), Transition metal" link="http://en.wikipedia.org/wiki/Rhenium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 76: Osmium (Os), Transition metal" link="http://en.wikipedia.org/wiki/Osmium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 77: Iridium (Ir), Transition metal" link="http://en.wikipedia.org/wiki/Iridium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 78: Platinum (Pt), Transition metal" link="http://en.wikipedia.org/wiki/Platinum"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 79: Gold (Au), Transition metal" link="http://en.wikipedia.org/wiki/Gold"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 80: Mercury (Hg), Transition metal" link="http://en.wikipedia.org/wiki/Mercury_(element)"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 81: Thallium (Tl), Other metal" link="http://en.wikipedia.org/wiki/Thallium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 82: Lead (Pb), Other metal" link="http://en.wikipedia.org/wiki/Lead"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 83: Bismuth (Bi), Other metal" link="http://en.wikipedia.org/wiki/Bismuth"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 84: Polonium (Po), Metalloid" link="http://en.wikipedia.org/wiki/Polonium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 85: Astatine (At), Halogen" link="http://en.wikipedia.org/wiki/Astatine"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 86: Radon (Rn), Noble gas" link="http://en.wikipedia.org/wiki/Radon"]]  ||
 * [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 87: Francium (Fr), Alkali metal" link="http://en.wikipedia.org/wiki/Francium"]] ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 88: Radium (Ra), Alkaline earth metal" link="http://en.wikipedia.org/wiki/Radium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 89: Actinium (Ac), Actinoid" link="http://en.wikipedia.org/wiki/Actinium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 90: Thorium (Th), Actinoid" link="http://en.wikipedia.org/wiki/Thorium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 91: Protactinium (Pa), Actinoid" link="http://en.wikipedia.org/wiki/Protactinium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 92: Uranium (U), Actinoid" link="http://en.wikipedia.org/wiki/Uranium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 93: Neptunium (Np), Actinoid" link="http://en.wikipedia.org/wiki/Neptunium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 94: Plutonium (Pu), Actinoid" link="http://en.wikipedia.org/wiki/Plutonium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 95: Americium (Am), Actinoid" link="http://en.wikipedia.org/wiki/Americium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 96: Curium (Cm), Actinoid" link="http://en.wikipedia.org/wiki/Curium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 97: Berkelium (Bk), Actinoid" link="http://en.wikipedia.org/wiki/Berkelium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 98: Californium (Cf), Actinoid" link="http://en.wikipedia.org/wiki/Californium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 99: Einsteinium (Es), Actinoid" link="http://en.wikipedia.org/wiki/Einsteinium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 100: Fermium (Fm), Actinoid" link="http://en.wikipedia.org/wiki/Fermium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 101: Mendelevium (Md), Actinoid" link="http://en.wikipedia.org/wiki/Mendelevium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 102: Nobelium (No), Actinoid" link="http://en.wikipedia.org/wiki/Nobelium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 103: Lawrencium (Lr), Actinoid" link="http://en.wikipedia.org/wiki/Lawrencium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 104: Rutherfordium (Rf), Transition metal" link="http://en.wikipedia.org/wiki/Rutherfordium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 105: Dubnium (Db), Transition metal" link="http://en.wikipedia.org/wiki/Dubnium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 106: Seaborgium (Sg), Transition metal" link="http://en.wikipedia.org/wiki/Seaborgium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 107: Bohrium (Bh), Transition metal" link="http://en.wikipedia.org/wiki/Bohrium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 108: Hassium (Hs), Transition metal" link="http://en.wikipedia.org/wiki/Hassium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 109: Meitnerium (Mt)" link="http://en.wikipedia.org/wiki/Meitnerium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 110: Darmstadtium (Ds)" link="http://en.wikipedia.org/wiki/Darmstadtium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 111: Roentgenium (Rg)" link="http://en.wikipedia.org/wiki/Roentgenium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 112: Copernicium (Cn), Transition metal" link="http://en.wikipedia.org/wiki/Copernicium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 113: Ununtrium (Uut)" link="http://en.wikipedia.org/wiki/Ununtrium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 114: Ununquadium (Uuq)" link="http://en.wikipedia.org/wiki/Ununquadium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 115: Ununpentium (Uup)" link="http://en.wikipedia.org/wiki/Ununpentium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 116: Ununhexium (Uuh)" link="http://en.wikipedia.org/wiki/Ununhexium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 117: Ununseptium (Uus)" link="http://en.wikipedia.org/wiki/Ununseptium"]]  ||  [[image:http://upload.wikimedia.org/wikipedia/commons/c/ce/Transparent.gif width="12" height="12" caption="Element 118: Ununoctium (Uuo)" link="http://en.wikipedia.org/wiki/Ununoctium"]]  ||
 * ~ Appearance ||
 * = Colorless gas, exhibiting a blue glow when placed in a high voltage electric field
 * = Colorless gas, exhibiting a blue glow when placed in a high voltage electric field
 * ~ General properties ||
 * ~ Name, [|symbol], [|number] || xenon, Xe, 54 ||
 * ~ Pronunciation ||  [|/] [|ˈ] [|z] [|ɛ] [|n] [|ɒ] [|n] [|/] [|//**zen**-on//] [|[1]]
 * ~ [|Element category] || [|noble gases] ||
 * ~ [|Group], [|period] , [|block] || [|18] , [|5] , [|p] ||
 * ~ [|Standard atomic weight] || 131.293(6) ||
 * ~ [|Electron configuration] || [ [|Kr] ] 5s2 4d10 5p6 ||
 * ~ Electrons per [|shell] || 2, 8, 18, 18, 8 ( [|Image] ) ||
 * ~ Physical properties ||
 * ~ [|Phase] || [|gas] ||
 * ~ [|Density] || (0 °C, 101.325 [|kPa] )
 * ~ Liquid [|density] at [|b.p.] || 3.057 [|[3]] g·cm−3 ||
 * ~ [|Melting point] || (101.325 kPa) 161.4 [|K] , -111.7 °C, -169.1 °F ||
 * ~ [|Boiling point] || (101.325 kPa) 165.03 K, -108.12 °C, -162.62 °F ||
 * ~ [|Triple point] || 161.405 K (-112°C), 81.6 [|[4]] kPa ||
 * ~ [|Critical point] || 289.77 K, 5.841 MPa ||
 * ~ [|Heat of fusion] || (101.325 kPa) 2.27 [|kJ·mol−1] ||
 * ~ [|Heat of vaporization] || (101.325 kPa) 12.64 kJ·mol−1 ||
 * ~ [|Molar heat capacity] || 5 [|R] /2 = 20.786 J·mol−1·K−1 ||
 * ~ [|Vapor pressure] ||
 * || P (Pa) || 1 || 10 || 100 || 1 k || 10 k || 100 k ||
 * at T (K) || 83 || 92 || 103 || 117 || 137 || 165 ||  ||
 * ~ Atomic properties ||
 * ~ [|Oxidation states] || 0, +1, +2, +4, +6, +8
 * ~ [|Electronegativity] || 2.6 (Pauling scale) ||
 * ~ [|Ionization energies] || 1st: 1170.4 kJ·mol−1 ||
 * ^  || 2nd: 2046.4 kJ·mol−1 ||
 * ^  || 3rd: 3099.4 kJ·mol−1 ||
 * ~ [|Covalent radius] || [|140±9] pm ||
 * ~ [|Van der Waals radius] || [|216] pm ||
 * ~ Miscellanea ||
 * ~ [|Crystal structure] || face-centered cubic ||
 * ~ [|Magnetic ordering] || [|diamagnetic] [|[5]] ||
 * ~ [|Thermal conductivity] || 5.65×10-3 W·m−1·K−1 ||
 * ~ [|Speed of sound] || (liquid) 1090 [|m/s] ; (gas) 169 [|m·s−1] ||
 * ~ [|CAS registry number] || 7440-63-3 ||
 * ~ Most stable isotopes ||
 * = Main article: [|Isotopes of xenon] ||
 * ||~ [|iso] ||~ [|NA] ||~ [|half-life] ||~ [|DM] ||~ [|DE] ( [|MeV] ) ||~ [|DP] ||
 * 124Xe || 0.095% |||||||| 124Xe is [|stable] with 70 [|neutrons] ||
 * 125Xe || [|syn] || 16.9 [|h] || [|ε] || 1.652 || 125 [|I] ||
 * 126Xe || 0.089% |||||||| 126Xe is [|stable] with 72 [|neutrons] ||
 * 127Xe || [|syn] || 36.345 [|d] || [|ε] || 0.662 || 127 [|I] ||
 * 128Xe || 1.91% |||||||| 128Xe is [|stable] with 74 [|neutrons] ||
 * 129Xe || 26.4% |||||||| 129Xe is [|stable] with 75 [|neutrons] ||
 * 130Xe || 4.07% |||||||| 130Xe is [|stable] with 76 [|neutrons] ||
 * 131Xe || 21.2% |||||||| 131Xe is [|stable] with 77 [|neutrons] ||
 * 132Xe || 26.9% |||||||| 132Xe is [|stable] with 78 [|neutrons] ||
 * 133Xe || [|syn] || 5.247 [|d] || [|β−] || 0.427 || 133 [|Cs] ||
 * 134Xe || 10.4% |||||||| 134Xe is [|stable] with 80 [|neutrons] ||
 * 135Xe || [|syn] || 9.14 [|h] || [|β−] || 1.16 || 135 [|Cs] ||
 * 136Xe || 8.86% || 2.11×1021y [|[6]] || [|β−β−] || - || 136 [|Ba] ||  ||
 * = * [|v]

Occurrence and production
Xenon is a [|trace gas] in [|Earth's atmosphere], occurring at 87±1 [|parts per billion] (nL/L), or approximately 1 part per 11.5 million, [|[48]] and is also found in gases emitted from some [|mineral springs]. Xenon is obtained commercially as a byproduct of the [|separation of air] into [|oxygen] and [|nitrogen]. After this separation, generally performed by [|fractional distillation] in a double-column plant, the [|liquid oxygen] produced will contain small quantities of krypton and xenon. By additional fractional distillation steps, the liquid oxygen may be enriched to contain 0.1–0.2% of a krypton/xenon mixture, which is extracted either via adsorption onto [|silica gel] or by distillation. Finally, the krypton/xenon mixture may be separated into [|krypton] and xenon via distillation. [|[49]] [|[50]] Extraction of a liter of xenon from the atmosphere requires 220 [|watt-hours] of energy. [|[51]] Worldwide production of xenon in 1998 was estimated at 5,000–7,000 m3. [|[52]] Because of its low abundance, xenon is much more expensive than the lighter noble gases—approximate prices for the purchase of small quantities in Europe in 1999 were 10 [|€] /L for xenon, 1 €/L for krypton, and 0.20 €/L for neon. [|[52]] Within the Solar System, the [|nucleon] fraction of xenon is 1.56 × 10−8, for an [|abundance] of one part in 64 million of the total mass. [|[53]] Xenon is relatively rare in the [|Sun] 's atmosphere, on [|Earth], and in [|asteroids] and [|comets]. The planet [|Jupiter] has an unusually high abundance of xenon in its atmosphere; about 2.6 times as much as the Sun. [|[54]] This high abundance remains unexplained and may have been caused by an early and rapid buildup of [|planetesimals] —small, subplanetary bodies—before the [|presolar disk] began to heat up. [|[55]] (Otherwise, xenon would not have been trapped in the planetesimal ices.) The problem of the low terrestrial xenon may potentially be explained by [|covalent bonding] of xenon to oxygen within [|quartz], hence reducing the outgassing of xenon into the atmosphere. [|[56]] Unlike the lower mass noble gases, the normal [|stellar nucleosynthesis] process inside a star does not form xenon. Elements more massive than [|iron-56] have a net energy cost to produce through fusion, so there is no energy gain for a star when creating xenon. [|[57]] Instead, xenon is formed during [|supernova] explosions, [|[58]] by the slow neutron capture process ( [|s-process] ) of [|red giant] stars that have exhausted the hydrogen at their cores and entered the [|asymptotic giant branch], [|[59]] in classical [|nova] explosions [|[60]] and from the radioactive decay of elements such as [|iodine] , [|uranium]

Isotopes and isotopic studies
Naturally occurring xenon is made of eight [|stable] [|isotopes], the most of any element with the exception of tin, which has ten. Xenon and tin are the only elements to have more than seven stable isotopes. [|[62]] The isotopes 124Xe and 134Xe are predicted to undergo [|double beta decay], but this has never been observed so they are considered to be stable. [|[63]] Besides these stable forms, there are over 40 unstable isotopes that have been studied. The longest lived these isotopes is 136Xe, which has been observed to undergo double beta decay with a half-life of 2.11 x 1021yr. [|[6]] 129Xe is produced by [|beta decay] of 129 [|I], which has a [|half-life] of 16 million years, while 131mXe, 133Xe, 133mXe, and 135Xe are some of the [|fission] products of both 235 [|U] and 239 [|Pu] , [|[61]] and therefore used as indicators of nuclear explosions. Nuclei of two of the stable [|isotopes of xenon], 129Xe and 131Xe, have non-zero intrinsic [|angular momenta] ( [|nuclear spins] , suitable for [|nuclear magnetic resonance] ). The nuclear spins can be aligned beyond ordinary polarization levels by means of circularly polarized light and [|rubidium] vapor. [|[64]] The resulting [|spin polarization] of xenon [|nuclei] can surpass 50% of its maximum possible value, greatly exceeding the equilibrium value dictated by the [|Boltzmann distribution] (typically 0.001% of the maximum value at [|room temperature], even in the strongest [|magnets] ). Such non-equilibrium alignment of spins is a temporary condition, and is called // [|hyperpolarization] //. The process of hyperpolarizing the xenon is called //optical pumping// (although the process is different from [|pumping a laser] ). [|[65]] Because a 129Xe nucleus has a [|spin] of 1/2, and therefore a zero [|electric] [|quadrupole moment], the 129Xe nucleus does not experience any quadrupolar interactions during collisions with other atoms, and thus its hyperpolarization can be maintained for long periods of time even after the laser beam has been turned off and the alkali vapor removed by condensation on a room-temperature surface. Spin polarization of 129Xe can persist from several [|seconds] for xenon atoms dissolved in [|blood] [|[66]] to several hours in the [|gas phase] [|[67]] and several days in deeply frozen solid xenon. [|[68]] In contrast, [|131Xe] has a nuclear spin value of 3/2 and a nonzero [|quadrupole moment], and has //T//1 relaxation times in the [|millisecond] and [|second] ranges. [|[69]] Some radioactive isotopes of xenon, for example, 133Xe and 135Xe, are produced by [|neutron] irradiation of fissionable material within [|nuclear reactors]. [|[8]] [|135Xe] is of considerable significance in the operation of [|nuclear fission reactors]. 135Xe has a huge [|cross section] for [|thermal neutrons], 2.6×106 [|barns] , [|[12]] so it acts as a [|neutron absorber] or " [|poison] " that can slow or stop the chain reaction after a period of operation. This was discovered in the earliest nuclear reactors built by the American [|Manhattan Project] for [|plutonium] production. Fortunately the designers had made provisions in the design to increase the reactor's reactivity (the number of neutrons per fission that go on to fission other atoms of [|nuclear fuel] ). [|[70]] 135Xe reactor poisoning played a major role in the [|Chernobyl disaster]. [|[71]] A shutdown or decrease of power of a reactor can result in buildup of 135Xe and getting the reactor into the [|iodine pit]. Under adverse conditions, relatively high concentrations of radioactive xenon isotopes may be found emanating from nuclear reactors due to the release of fission products from cracked [|fuel rods], [|[72]] or fissioning of uranium in [|cooling water]. [|[73]] Because xenon is a tracer for two parent isotopes, xenon isotope ratios in [|meteorites] are a powerful tool for studying the [|formation of the solar system]. The [|iodine-xenon method] of [|dating] gives the time elapsed between [|nucleosynthesis] and the condensation of a solid object from the [|solar nebula]. In 1960, physicist [|John H. Reynolds] discovered that certain [|meteorites] contained an isotopic anomaly in the form of an overabundance of xenon-129. He inferred that this was a [|decay product] of radioactive [|iodine-129]. This isotope is produced slowly by [|cosmic ray spallation] and [|nuclear fission], but is produced in quantity only in supernova explosions. As the half-life of 129I is comparatively short on a cosmological time scale, only 16 million years, this demonstrated that only a short time had passed between the supernova and the time the meteorites had solidified and trapped the 129I. These two events (supernova and solidification of gas cloud) were inferred to have happened during the early history of the [|Solar System], as the 129I isotope was likely generated before the Solar System was formed, but not long before, and seeded the solar gas cloud with isotopes from a second source. This supernova source may also have caused collapse of the solar gas cloud. [|[74]] [|[75]] In a similar way, xenon isotopic ratios such as 129Xe/130Xe and 136Xe/130Xe are also a powerful tool for understanding planetary differentiation and early outgassing. [|[11]] For example, The [|atmosphere of Mars] shows a xenon abundance similar to that of Earth: 0.08 parts per million, [|[76]] however Mars shows a higher proportion of 129Xe than the Earth or the Sun. As this isotope is generated by radioactive decay, the result may indicate that Mars lost most of its primordial atmosphere, possibly within the first 100 million years after the planet was formed. [|[77]] [|[78]] In another example, excess 129Xe found in [|carbon dioxide] well gases from [|New Mexico] was believed to be from the decay of [|mantle] -derived gases soon after Earth's formation. [|[61]] [|[79]]

Compounds
After Neil Bartlett's discovery in 1962 that xenon can form chemical compounds, a large number of xenon compounds have been discovered and described. Almost all known xenon compounds contain the [|electronegative] atoms fluorine or oxygen. [|[80]]

Halides
[|Xenon tetrafluoride]          XeF4 crystals, 1962 Three [|fluorides] are known: [|XeF2], [|XeF4] , and [|XeF6]. The fluorides are the starting point for the synthesis of almost all xenon compounds. The solid, crystalline difluoride XeF2 is formed when a mixture of [|fluorine] and xenon gases is exposed to ultraviolet light. [|[81]] Ordinary daylight is sufficient. [|[82]] Long-term heating of XeF2 at high temperatures under an NiF2 catalyst yields XeF6. [|[83]] Pyrolysis of XeF6 in the presence of [|NaF] yields high-purity XeF4. [|[84]] The xenon fluorides behave as both fluoride acceptors and fluoride donors, forming salts that contain such cations as XeF+ and Xe2F3+, and anions such as XeF5−, XeF7−, and XeF82−. The green, paramagnetic Xe2+ is formed by the reduction of XeF2 by xenon gas. [|[80]] XeF2 is also able to form [|coordination complexes] with transition metal ions. Over 30 such complexes have been synthesized and characterized. [|[83]] Whereas the xenon fluorides are well-characterized, the other halides are not known, the only exception being the dichloride, [|XeCl2]. Xenon dichloride is reported to be an endothermic, colorless, crystalline compound that decomposes into the elements at 80°C, formed by the high-frequency irradiation of a mixture of xenon, fluorine, and [|silicon] or [|carbon tetrachloride]. [|[85]] However, doubt has been raised as to whether XeCl2 is a real compound and not merely a [|van der Waals molecule] consisting of weakly bound Xe atoms and Cl2 molecules. [|[86]] Theoretical calculations indicate that the linear molecule XeCl2 is less stable than the van der Waals complex. [|[87]]

Oxides and oxohalides
Three oxides of xenon are known: [|xenon trioxide] ( XeO3 ) and [|xenon tetroxide] ( XeO4 ), both of which are dangerously explosive and powerful oxidizing agents. Xenon dioxide (XeO2) was reported in 2011 with a [|coordination number] of four. [|[88]] XeO2 forms when xenon fluoride is poured over ice. Its crystal structure may allow it to replace silicon in silicate minerals. [|[89]] XeOO+ cation has been identified by [|infrared spectroscopy] in solid [|argon]. [|[90]] Xenon does not react with oxygen directly; the trioxide is formed by the hydrolysis of XeF6 : [|[91]] XeF6 + 3 H2O → XeO3 + 6 HF  XeO3 is weakly acidic, dissolving in alkali to form unstable //xenate// salts containing the HXeO − 4 anion. These unstable salts easily [|disproportionate] into xenon gas and // [|perxenate] // salts, containing the XeO 4− 6 anion. [|[92]]

Barium perxenate, when treated with concentrated [|sulfuric acid], yields gaseous xenon tetroxide: [|[85]] Ba2XeO6 + 2 H2SO4 → 2 BaSO4 + 2 H2O + XeO4 To prevent decomposition, the xenon tetroxide thus formed is quickly cooled to form a pale-yellow solid. It explodes above −35.9 °C into xenon and oxygen gas. A number of xenon oxyfluorides are known, including XeOF2, [|XeOF4] , XeO2F2 , and XeO3F2. XeOF2 is formed by the reaction of [|OF2] with xenon gas at low temperatures. It may also be obtained by the partial hydrolysis of XeF4. It disproportionates at −20 °C into XeF2 and XeO2F2. [|[93]] XeOF4 is formed by the partial hydrolysis of XeF6, [|[94]] or the reaction of XeF6 with sodium perxenate, Na4XeO6. The latter reaction also produces a small amount of XeO3F2. XeOF4 reacts with [|CsF] to form the XeOF − 5 anion, [|[93]] [|[95]] while XeOF3 reacts with the alkali metal fluorides [|KF], [|RbF] and CsF to form the XeOF − 4 anion. [|[96]]

Other compounds
Recently, there has been an interest in xenon compounds where xenon is directly bonded to a less electronegative element than fluorine or oxygen, particularly [|carbon]. [|[97]] Electron-withdrawing groups, such as groups with fluorine substitution, are necessary to stabilize these compounds. [|[92]] Numerous such compounds have been characterized, including: [|[93]] [|[98]] > 5 or [|//tert//-butyl]. > 2  Other compounds containing xenon bonded to a less electronegative element include F–Xe–N(SO2F)2 and F–Xe–BF2. The latter is synthesized from [|dioxygenyl] tetrafluoroborate, O2BF4, at −100 °C. [|[93]] [|[99]] An unusual ion containing xenon is the [|tetraxenonogold(II)] cation, AuXe 2+ 4, which contains Xe–Au bonds. [|[100]] This ion occurs in the compound AuXe4(Sb2F11)2, and is remarkable in having direct chemical bonds between two notoriously unreactive atoms, xenon and [|gold] , with xenon acting as a transition metal ligand.
 * C6F5–Xe+–N≡C–CH3, where C6F5 is the pentafluorophenyl group.
 * [C6F5]2Xe
 * C6F5–Xe–X, where X is [|CN] , F, or Cl.
 * R–C≡C–Xe+, where R is C2F −
 * C6F5–XeF +
 * (C6F5Xe)2Cl+

In 1995, M. Räsänen and co-workers, scientists at the [|University of Helsinki] in [|Finland], announced the preparation of xenon dihydride (HXeH), and later xenon hydride-hydroxide (HXeOH), hydroxenoacetylene (HXeCCH), and other Xe-containing molecules. [|[101]] In 2008, Khriachtchev //et al.// reported the preparation of HXeOXeH by the [|photolysis] of water within a [|cryogenic] xenon matrix. [|[102]] [|Deuterated] molecules, HXeOD and DXeOH, have also been produced.

Clathrates and excimers
In addition to compounds where xenon forms a [|chemical bond], xenon can form [|clathrates] —substances where xenon atoms are trapped by the [|crystalline lattice] of another compound. An example is [|xenon hydrate] (Xe·5.75 H2O), where xenon atoms occupy vacancies in a lattice of water molecules. [|[104]] This clathrate has a melting point of 24 °C. [|[105]] The [|deuterated] version of this hydrate has also been produced. [|[106]] Such [|clathrate hydrates] can occur naturally under conditions of high pressure, such as in [|Lake Vostok] underneath the [|Antarctic] ice sheet. [|[107]] Clathrate formation can be used to fractionally distill xenon, argon and krypton. [|[108]] Xenon can also form [|endohedral fullerene] compounds, where a xenon atom is trapped inside a [|fullerene] molecule. The xenon atom trapped in the fullerene can be monitored via 129Xe [|nuclear magnetic resonance] (NMR) spectroscopy. Using this technique, chemical reactions on the fullerene molecule can be analyzed, due to the sensitivity of the [|chemical shift] of the xenon atom to its environment. However, the xenon atom also has an electronic influence on the reactivity of the fullerene. [|[109]] While xenon atoms are at their [|ground energy state], they repel each other and will not form a bond. When xenon atoms becomes energized, however, they can form an [|excimer] (excited dimer) until the electrons return to the [|ground state]. This entity is formed because the xenon atom tends to fill its outermost [|electronic shell], and can briefly do this by adding an electron from a neighboring xenon atom. The typical lifetime of a xenon excimer is 1–5 ns, and the decay releases [|photons] with [|wavelengths] of about 150 and 173 [|nm]. [|[110]] [|[111]] Xenon can also form excimers with other elements, such as the [|halogens] [|bromine], [|chlorine] and [|fluorine].

[ [|edit] ] Gas-discharge lamps
Xenon is used in light-emitting devices called xenon flash lamps, which are used in [|photographic flashes] and stroboscopic lamps; [|[13]] to excite the [|active medium] in [|lasers] which then generate [|coherent light] ; [|[113]] and, occasionally, in [|bactericidal] lamps. [|[114]] The first solid-state [|laser], invented in 1960, was pumped by a xenon flash lamp, [|[17]] and lasers used to power [|inertial confinement fusion] are also pumped by xenon flash lamps. [|[115]] Xenon short-arc lamp         Xenon gas discharge tube Continuous, short-arc, high pressure [|xenon arc lamps] have a [|color temperature] closely approximating noon sunlight and are used in [|solar simulators]. That is, the [|chromaticity] of these lamps closely approximates a heated [|black body] radiator that has a temperature close to that observed from the Sun. After they were first introduced during the 1940s, these lamps began replacing the shorter-lived [|carbon arc lamps] in movie projectors. [|[14]] They are employed in typical [|35mm] and [|IMAX] [|film projection] systems, automotive [|HID] headlights, high-end [|"tactical" flashlights] and other specialized uses. These arc lamps are an excellent source of short wavelength [|ultraviolet] radiation and they have intense emissions in the near [|infrared], which is used in some [|night vision] systems. The individual cells in a [|plasma display] use a mixture of xenon and neon that is converted into a [|plasma] using [|electrodes]. The interaction of this plasma with the electrodes generates ultraviolet [|photons], which then excite the [|phosphor] coating on the front of the display. [|[116]] [|[117]] Xenon is used as a "starter gas" in [|high pressure sodium lamps]. It has the lowest [|thermal conductivity] and lowest [|ionization potential] of all the non-radioactive noble gases. As a noble gas, it does not interfere with the chemical reactions occurring in the operating lamp. The low thermal conductivity minimizes thermal losses in the lamp while in the operating state, and the low ionization potential causes the [|breakdown voltage] of the gas to be relatively low in the cold state, which allows the lamp to be more easily started. [|[118]]

[ [|edit] ] Lasers
In 1962, a group of researchers at [|Bell Laboratories] discovered laser action in xenon, [|[119]] and later found that the laser gain was improved by adding [|helium] to the lasing medium. [|[120]] [|[121]] The first [|excimer laser] used a xenon [|dimer] (Xe2) energized by a beam of electrons to produce [|stimulated emission] at an [|ultraviolet] wavelength of 176 [|nm]. [|[16]] Xenon chloride and xenon fluoride have also been used in excimer (or, more accurately, exciplex) lasers. [|[122]] The xenon chloride excimer laser has been employed, for example, in certain dermatological uses.

Precautions
Many oxygen-containing [|xenon compounds] are toxic due to their strong [|oxidative] properties, and explosive due to their tendency to break down into elemental xenon plus diatomic oxygen (O2), which contains much stronger chemical bonds than the xenon compounds. [|[158]] Xenon gas can be safely kept in normal sealed glass or metal containers at [|standard temperature and pressure]. However, it readily dissolves in most plastics and rubber, and will gradually escape from a container sealed with such materials. [|[159]] Xenon is non- [|toxic], although it does dissolve in blood and belongs to a select group of substances that penetrate the [|blood-brain barrier] , causing mild to full surgical [|anesthesia] when inhaled in high concentrations with oxygen. [|[158]] At 169 m/s, the [|speed of sound] in xenon gas is slower than that in air [|[160]] due to the slower average speed of the heavy xenon atoms compared to nitrogen and oxygen molecules. Hence, xenon lowers the resonant frequencies of the [|vocal tract] when inhaled. This produces a characteristic lowered voice timbre, an effect opposite to the high-timbred voice caused by inhalation of [|helium]. Like helium, xenon does not satisfy the body's need for oxygen. Xenon is both a simple [|asphyxiant] and an anesthetic more powerful than nitrous oxide; consequently, many universities no longer allow the voice stunt as a general chemistry demonstration. As xenon is expensive, the gas [|sulfur hexafluoride], which is similar to xenon in molecular weight (146 versus 131), is generally used in this stunt, and is an asphyxiant without being anesthetic. [|[161]] It is possible to safely breathe heavy gases such as xenon or sulfur hexafluoride when they are in a mixture with oxygen; the oxygen comprising at least 20% of the mixture. Xenon at 80% concentration along with 20% oxygen rapidly produces the unconsciousness of general anesthesia (and has been used for this, as discussed above). Breathing mixes gases of different densities very effectively and rapidly so that heavier gases are purged along with the oxygen, and do not accumulate at the bottom of the lungs. [|[162]] There is, however, a danger associated with any heavy gas in large quantities: it may sit invisibly in a container, and if a person enters a container filled with an odorless, colorless gas, they may find themselves breathing it unknowingly. Xenon is rarely used in large enough quantities for this to be a concern, though the potential for danger exists any time a tank or container of xenon is kept in an unventilated space.