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Xenon is a chemical element; it has symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the formation of xenon hexafluoroplatinate, the first noble gas compound to be synthesized.
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 laser pumping. Xenon is also used to search for hypothetical weakly interacting massive particles and as a propellant for in spacecraft.
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 .
During the 1930s, American engineer Harold Edgerton began exploring strobe light technology for high speed photography. This led him to the invention of the xenon Flashtube in which light is generated by passing brief electric current through a tube filled with xenon gas. In 1934, Edgerton was able to generate flashes as brief as one microsecond with this method.
In 1939, American physician Albert R. Behnke Jr. began exploring the causes of "drunkenness" in deep-sea divers. He tested the effects of varying the breathing mixtures on his subjects, and discovered that this caused the divers to perceive a change in depth. From his results, he deduced that xenon gas could serve as an Anesthesia. Although Russian toxicologist Nikolay Lazarev apparently studied xenon anesthesia in 1941, the first published report confirming xenon anesthesia was in 1946 by American medical researcher John H. Lawrence, who experimented on mice. Xenon was first used as a surgical anesthetic in 1951 by American anesthesiologist Stuart C. Cullen, who successfully used it with two patients. Xenon and the other noble gases were for a long time considered to be completely chemically inert and not able to form compounds. However, while teaching at the University of British Columbia, Neil Bartlett discovered that the gas platinum hexafluoride (PtF6) was a powerful Redox agent that could oxidize oxygen gas (O2) to form dioxygenyl hexafluoroplatinate (). Since O2 (1165 kJ/mol) and xenon (1170 kJ/mol) have almost the same first ionization potential, Bartlett realized that platinum hexafluoride might also be able to oxidize xenon. On March 23, 1962, he mixed the two gases and produced the first known compound of a noble gas, xenon hexafluoroplatinate.
Bartlett thought its composition to be Xe+PtF6−, but later work revealed that it was probably a mixture of various xenon-containing salts.; translation of Lehrbuch der Anorganischen Chemie, founded by A. F. Holleman, continued by Egon Wiberg, edited by Nils Wiberg, Berlin: de Gruyter, 1995, 34th edition, . Since then, many other xenon compounds have been discovered, in addition to some compounds of the noble gases argon, krypton, and radon, including argon fluorohydride (HArF), krypton difluoride (KrF2), and Radon difluoride. By 1971, more than 80 xenon compounds were known.
In November 1989, IBM scientists demonstrated a technology capable of manipulating individual . The program, called IBM in atoms, used a scanning tunneling microscope to arrange 35 individual xenon atoms on a substrate of chilled crystal of nickel to spell out the three-letter company initialism. It was the first-time atoms had been precisely positioned on a flat surface.Browne, Malcolm W. (April 5, 1990) "2 Researchers Spell 'I.B.M.,' Atom by Atom". The New York Times
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 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.
Liquid or solid xenon can be formed at room temperature by implanting Xe+ ions into a solid matrix. Many solids have lattice constants smaller than solid Xe. This results in compression of the implanted Xe to pressures that may be sufficient for its liquefaction or solidification.
Xenon is a member of the zero-valence elements that are called noble gas or . 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.
In a gas-filled tube, xenon emits a blue or lavenderish glow when excited by Electric arc. Xenon emits a band of Spectral line that span the visual spectrum, but the most intense lines occur in the region of blue light, producing the coloration.
Worldwide production of xenon in 1998 was estimated at . (2025). 9783527201655, Wiley. ISBN 9783527201655 At a density of this is equivalent to roughly . Because of its scarcity, xenon is much more expensive than the lighter noble gases—approximate prices for the purchase of small quantities in Europe in 1999 were 10 Euro/L (=~€1.7/g) for xenon, 1 €/L (=~€0.27/g) for krypton, and 0.20 €/L (=~€0.22/g) for neon, while the much more plentiful argon, which makes up over 1% by volume of earth's atmosphere, costs less than a cent per liter.
Stable or extremely long lived isotopes of xenon are also produced in appreciable quantities in nuclear fission. Xenon-136 is produced both as a fission product and when xenon-135 undergoes neutron capture before it can decay. The ratio of xenon-136 to xenon-135 (or its decay products) can give hints as to the power history of a given reactor or identify a nuclear explosion, as xenon-135 is mostly produced by successive beta decays of more neutron-rich fission products. These short-lived nuclides do not share its neutron-absorbing prowess, and so absorb fewer neutrons during the brief moment of a nuclear explosion, lowering the ratio of mass-136 to mass-135 products.
The stable isotope xenon-132 has a fission product yield of over 4% in the thermal neutron fission of which means that stable or nearly stable xenon isotopes have a higher mass fraction in spent nuclear fuel (which is about 3% fission products) than it does in air. However, there is as of 2022 no commercial effort to extract xenon from spent fuel during nuclear reprocessing.
More than 40 unstable isotopes are known. The longest-lived of these isotopes are the primordial 124Xe, which undergoes double electron capture with a half-life of , and 136Xe, which undergoes double beta decay with a half-life of .
129Xe is produced by beta decay of 129iodine, which has a half-life of 16.1 million years. 131mXe, 133Xe, 133mXe, and 135Xe are some of the nuclear fission products of 235uranium and 239plutonium, and are used to detect and monitor nuclear explosions.
Because a 129Xe nucleus has a spin of 1/2, and therefore a zero electric field quadrupole moment, the 129Xe nucleus does not experience any quadrupolar interactions during collisions with other atoms, and the hyperpolarization persists for long periods even after the engendering light and vapor have been removed. Spin polarization of 129Xe can persist from several for xenon atoms dissolved in blood to several hours in the gas phase and several days in deeply frozen solid xenon. In contrast, 131Xe has a nuclear spin value of and a nonzero quadrupole moment, and has t1 relaxation times in the millisecond and second ranges.
135Xe reactor poisoning was a major factor in the Chernobyl disaster. A shutdown or decrease of power of a reactor can result in buildup of 135Xe, with reactor operation going into a condition known as the iodine pit. Under adverse conditions, relatively high concentrations of radioactive xenon isotopes may emanate from cracked , or fissioning of uranium in Water cooling.
Isotope ratios of xenon produced in natural nuclear fission reactors at Oklo in Gabon reveal the reactor properties during the chain reaction that took place about 2 billion years ago.
Because the half-life of 129I is comparatively short on a cosmological time scale (~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, because the 129I isotope was likely generated shortly before the Solar System was formed, seeding the solar gas cloud with isotopes from a second source. This supernova source may also have caused collapse of the solar gas cloud.
In a similar way, xenon isotopic ratios such as 129Xe/130Xe and 136Xe/130Xe are a powerful tool for understanding planetary differentiation and early outgassing. For example, the atmosphere of Mars shows a xenon abundance similar to that of Earth (0.08 parts per million) but Mars shows a greater abundance of 129Xe than the Earth or the Sun. Since 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. In another example, excess 129Xe found in carbon dioxide well gases from New Mexico is believed to be from the decay of mantle-derived gases from soon after Earth's formation.
The solid, crystalline difluoride is formed when a mixture of fluorine and xenon gases is exposed to ultraviolet light. The ultraviolet component of ordinary daylight is sufficient. Long-term heating of at high temperatures under an catalyst yields . Pyrolysis of in the presence of sodium fluoride yields high-purity .
The xenon fluorides behave as both fluoride acceptors and fluoride donors, forming salts that contain such cations as and , and anions such as , , and . The green, paramagnetic is formed by the reduction of by xenon gas.
also forms coordination complexes with transition metal ions. More than 30 such complexes have been synthesized and characterized.
Whereas the xenon fluorides are well characterized, the other halides are not. Xenon dichloride, formed by the high-frequency irradiation of a mixture of xenon, fluorine, and silicon or carbon tetrachloride, is reported to be an endothermic, colorless, crystalline compound that decomposes into the elements at 80 °C. However, may be merely a van der Waals molecule of weakly bound Xe atoms and molecules and not a real compound. Theoretical calculations indicate that the linear molecule is less stable than the van der Waals complex. Xenon tetrachloride and xenon dibromide are even more unstable and they cannot be synthesized by chemical reactions. They were created by radioactive decay of and , respectively. (2025). 9781483157368, Elsevier Science. ISBN 9781483157368
Xenon does not react with oxygen directly; the trioxide is formed by the hydrolysis of :
is weakly acidic, dissolving in alkali to form unstable ''xenate'' salts containing the anion. These unstable salts easily disproportionate into xenon gas and [[perxenate]] salts, containing the anion.
Barium perxenate, when treated with concentrated sulfuric acid, yields gaseous xenon tetroxide:
To prevent decomposition, the xenon tetroxide thus formed is quickly cooled into a pale-yellow solid. It explodes above −35.9 °C into xenon and oxygen gas, but is otherwise stable.
A number of xenon oxyfluorides are known, including , , , and . is formed by reacting with xenon gas at low temperatures. It may also be obtained by partial hydrolysis of . It disproportionates at −20 °C into and . is formed by the partial hydrolysis of ...
is also formed by partial hydrolysis of .
reacts with [[CsF|caesium fluoride]] to form the anion, while XeOF3 reacts with the alkali metal fluorides KF, RbF and CsF to form the anion.
Other compounds containing xenon bonded to a less electronegative element include and . The latter is synthesized from dioxygenyl tetrafluoroborate, , at −100 °C.
An unusual ion containing xenon is the tetraxenonogold(II) cation, , which contains Xe–Au bonds. This ion occurs in the compound , and is remarkable in having direct chemical bonds between two notoriously unreactive atoms, xenon and gold, with xenon acting as a transition metal ligand. A similar mercury complex (HgXe)(Sb3F17) (formulated as HgXe2+Sb2F11–SbF6–) is also known.
The compound contains a Xe–Xe bond, the longest element-element bond known (308.71 pm = 3.0871 Angstrom).
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. In 2008, Khriachtchev et al. reported the preparation of HXeOXeH by the photolysis of water within a cryogenic xenon matrix. Deuterium molecules, HXeOD and DXeOH, have also been produced.
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 observed by 129Xe nuclear magnetic resonance (NMR) spectroscopy. Through the sensitive chemical shift of the xenon atom to its environment, chemical reactions on the fullerene molecule can be analyzed. These observations are not without caveat, however, because the xenon atom has an electronic influence on the reactivity of the fullerene.
When xenon atoms are in the stationary 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 complete the outermost Electron shell by adding an electron from a neighboring xenon atom. The typical lifetime of a xenon excimer is 1–5 nanoseconds, and the decay releases with of about 150 and 173 Nanometre. Xenon can also form excimers with other elements, such as the bromine, chlorine, and fluorine.
Continuous, short-arc, high pressure xenon arc lamps have a color temperature closely approximating noon sunlight and are used in Solar Simulator. That is, the chromaticity of these lamps closely approximates a heated black body radiator at the temperature of the Sun. First introduced in the 1940s, these lamps replaced the shorter-lived carbon arc lamps in movie projectors. They are also employed in typical 35mm, IMAX, and digital Movie projector systems. They are an excellent source of short wavelength ultraviolet radiation and have intense emissions in the near infrared used in some night vision systems. Xenon is used as a starter gas in metal halide lamps for HID Headlight, and high-end tactical light.
The individual cells in a plasma display contain a mixture of xenon and neon ionized with . The interaction of this plasma with the electrodes generates ultraviolet , which then excite the phosphor coating on the front of the display.
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.
Xenon interacts with many different receptors and ion channels, and like many theoretically multi-modal inhalation anesthetics, these interactions are likely complementary. Xenon is a high-affinity glycine-site NMDA receptor antagonist. However, xenon is different from certain other NMDA receptor antagonists in that it is not neurotoxicity and it inhibits the neurotoxicity of ketamine and nitrous oxide (N2O), while actually producing neuroprotection. Unlike ketamine and nitrous oxide, xenon does not stimulate a dopamine efflux in the nucleus accumbens.
Like nitrous oxide and cyclopropane, xenon activates the two-pore domain potassium channel TREK-1. A related channel TASK-3 also implicated in the actions of inhalation anesthetics is insensitive to xenon. Xenon inhibits nicotinic acetylcholine α4β2 receptors which contribute to spinally mediated analgesia. Xenon is an effective inhibitor of plasma membrane Ca2+ ATPase. Xenon inhibits Ca2+ ATPase by binding to a hydrophobic pore within the enzyme and preventing the enzyme from assuming active conformations.
Xenon is a competitive inhibitor of the serotonin 5-HT3 receptor. While neither anesthetic nor antinociceptive, this reduces anesthesia-emergent nausea and vomiting.
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 with oxygen in concentrations that have a lower risk of hypoxia. Unlike nitrous oxide, xenon is not a greenhouse gas and is viewed as environmentally friendly. Though recycled in modern systems, xenon vented to the atmosphere is only returning to its original source, without environmental impact.
In 2025, four UK mountaineers, including Alistair Carns, climbed Mount Everest in an expedition lasting only one week, claiming their inhalation of xenon gas to stimulate erythropoietin production had obviated the usual several weeks' altitude acclimatisation. The International Climbing and Mountaineering Federation (UIAA) criticised the decision, citing that there is no evidence that the inhalation of xenon improves performance in high elevation environments. Furthermore, the UIAA warned that as an anesthetic, xenon gas could result in impaired brain function, respiratory compromise, and death if used in an unmonitored setting.
Xenon, particularly hyperpolarized 129Xe, is a useful contrast agent for MRI (MRI). In the gas phase, it can image cavities in a porous sample, alveoli in lungs, or the flow of gases within the lungs. Because xenon is soluble both in water and in hydrophobic solvents, it can image various soft living tissues.
Xenon-129 is used as a visualization agent in MRI scans. When a patient inhales hyperpolarized xenon-129 ventilation and gas exchange in the lungs can be imaged and quantified. Unlike xenon-133, xenon-129 is non-ionizing and is safe to be inhaled with no adverse effects.
Hyperpolarized xenon can be used by Surface science. Normally, it is difficult to characterize surfaces with NMR because signals from a surface are overwhelmed by signals from the atomic nuclei in the bulk of the sample, which are much more numerous than surface nuclei. However, nuclear spins on solid surfaces can be selectively polarized by transferring spin polarization to them from hyperpolarized xenon gas. This makes the surface signals strong enough to measure and distinguish from bulk signals.
Liquid xenon is used in calorimeters to measure , and as a detector of hypothetical weakly interacting massive particles, or WIMPs. When a WIMP collides with a xenon nucleus, theory predicts it will impart enough energy to cause ionization and scintillation. Liquid xenon is useful for these experiments because its density makes dark matter interaction more likely and it permits a quiet detector through self-shielding.
Xenon is the preferred propellant for ion propulsion of spacecraft because it has low ionization potential per Atomic mass and can be stored as a liquid at near room temperature (under high pressure), yet easily evaporated to feed the engine. Xenon is inert, environmentally friendly, and less corrosive to an ion engine than other fuels such as mercury or caesium. Xenon was first used for satellite ion engines during the 1970s. It was later employed as a propellant for JPL's Deep Space 1 probe, Europe's SMART-1 spacecraft and for the three ion propulsion engines on NASA's Dawn Spacecraft.
Chemically, the perxenate compounds are used as in analytical chemistry. Xenon difluoride is used as an etchant for silicon, particularly in the production of microelectromechanical systems (MEMS). The anticancer drug Fluorouracil can be produced by reacting xenon difluoride with uracil. Xenon is also used in protein crystallography. Applied at pressures from 0.5 to 5 MPa (5 to 50 atm) to a protein crystal, xenon atoms bind in predominantly Hydrophobe cavities, often creating a high-quality, isomorphous, heavy-atom derivative that can be used for solving the phase problem.
The speed of sound in xenon gas (169 m/s) is less than that in air169.44 m/s in xenon (at and 107 kPa), compared to 344 m/s in air. See: because the average velocity of the heavy xenon atoms is less than that of nitrogen and oxygen molecules in air. Hence, xenon vibrates more slowly in the vocal tract when exhaled and produces lowered voice tones (low-frequency-enhanced sounds, but the fundamental frequency or pitch does not change), an effect opposite to the high-toned voice produced in helium. Specifically, when the vocal tract is filled with xenon gas, its natural resonant frequency becomes lower than when it is filled with air. Thus, the low frequencies of the sound wave produced by the same direct vibration of the vocal cords would be enhanced, resulting in a change of the timbre of the sound amplified by the vocal tract. Like helium, xenon does not satisfy the body's need for oxygen, and it is both a simple asphyxiant gas and an anesthetic more powerful than nitrous oxide; consequently, and because xenon is expensive, many universities have prohibited the voice stunt as a general chemistry demonstration. The gas sulfur hexafluoride is similar to xenon in molecular weight (146 versus 131), less expensive, and though an asphyxiant, not toxic or anesthetic; it is often substituted in these demonstrations.
Dense gases such as xenon and sulfur hexafluoride can be breathed safely when mixed with at least 20% oxygen. Xenon at 80% concentration along with 20% oxygen rapidly produces the unconsciousness of general anesthesia. 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. There is, however, a danger associated with any heavy gas in large quantities: it may sit invisibly in a container, and a person who enters an area filled with an odorless, colorless gas may be asphyxiated without warning. 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.
Water-soluble xenon compounds such as monosodium xenate are moderately toxic, but have a very short half-life of the body – injected xenate is reduced to elemental xenon in about a minute.
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