Xenon

Xenon
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For other uses, see Xenon (disambiguation).
54 iodine ← xenon → caesium
Kr
↑
Xe
↓
Rn
Periodic Table - Extended Periodic Table


General
Name, Symbol, Number xenon, Xe, 54
Chemical series noble gases
Group, Period, Block 18, 5, p
Appearance colorless

Standard atomic weight 131.293(6)  g·mol−1
Electron configuration [Kr] 4d10 5s2 5p6
Electrons per shell 2, 8, 18, 18, 8
Physical properties
Phase gas
Density (0 °C, 101.325 kPa)
5.894 g/L
Melting point 161.4 K
(-111.7 °C, -169.1 °F)
Boiling point 165.03 K
(-108.12 °C, -162.62 °F)
Triple point 161.405 K, 81.6 kPa[1]
Critical point 289.77 K, 5.841 MPa
Heat of fusion 2.27  kJ·mol−1
Heat of vaporization 12.64  kJ·mol−1
Heat capacity (25 °C) 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
Crystal structure cubic face centered
Oxidation states 0, +1, +2, +4, +6, +8
(rarely more than 0)
(weakly acidic oxide)
Electronegativity 2.6 (scale Pauling)
Ionization energies 1st: 1170.4 kJ/mol
2nd: 2046.4 kJ/mol
3rd: 3099.4 kJ/mol
Atomic radius (calc.) 108  pm
Covalent radius 130  pm
Van der Waals radius 216 pm
Miscellaneous
Magnetic ordering nonmagnetic
Thermal conductivity (300 K) 5.65 m W·m−1·K−1
Speed of sound (liquid) 1090 m/s
CAS registry number 7440-63-3
Selected isotopes
Main article: Isotopes of xenon iso NA half-life DM DE (MeV) DP
124Xe 0.1% 1.1×1017y ε ε no data 124Te
125Xe syn 16.9 h ε 1.652 125I
126Xe 0.09% Xe is stable with 72 neutrons
127Xe syn 36.4 d ε 0.662 127I
128Xe 1.91% Xe is stable with 74 neutrons
129Xe 26.4% Xe is stable with 75 neutrons
130Xe 4.1% Xe is stable with 76 neutrons
131Xe 21.29% Xe is stable with 77 neutrons
132Xe 26.9% Xe is stable with 78 neutrons
133Xe syn 5.243 d Beta- 0.427 133Cs
134Xe 10.4% Xe is stable with 80 neutrons
135Xe syn 9.10 h Beta- 1.16 135Cs
136Xe 8.9% 2.36×1021y Beta- no data 136Ba

References
Xenon (IPA: /ˈzɛnɒn, ˈziːnɒn/) is a chemical element that has the symbol Xe and atomic number 54. A colorless, heavy, odorless noble gas, xenon occurs in the earth's atmosphere in trace amounts and was part of the first noble gas compound synthesized.[2][3]

Contents [hide]
1 Notable characteristics
2 Applications
3 History
4 Occurrence
5 Compounds
6 Isotopes
7 Precautions
8 References
9 External links



[edit] Notable characteristics
Xenon is a member of the zero-valence elements that are called noble or inert gases; however, "inert" may not be an entirely accurate description of this chemical series since at least 80 compounds of this noble gas have been synthesized. In a gas filled tube, xenon emits a blue glow when the gas is excited by electrical discharge. Using gigapascals of pressure, xenon has been forced into a metallic phase.[4] Xenon can also form clathrates with water when atoms of it are trapped in a lattice of the water molecules.


[edit] Applications

Xenon in shaped Geissler tubes.This gas is most widely and most famously used in light-emitting devices called Xenon flash lamps, which are used in photographic flashes and stroboscopic lamps, to excite the active medium in lasers which then generate coherent light, to produce laser power for inertial confinement fusion, in bactericidal lamps (rarely), and in certain dermatological uses. Continuous, short-arc, high pressure Xenon arc lamps have a color temperature closely approximating noon sunlight and are used in solar simulators, typical 35mm and IMAX film projection systems, automotive HID headlights and other specialized uses. They are an excellent source of short wavelength ultraviolet radiation and they have intense emissions in the near infrared, which are used in some night vision systems. Other uses of Xenon:

Has been used as a general anesthetic, though it is expensive. Even so, anesthesia machines that can deliver Xenon are about to appear on the European market. [5] Two kinds of mechanism have been proposed. The first one involves the inhibition of the calcium ATPase pump in synaptic plasma membranes,[6] which results from a conformational change when xenon binds to nonpolar sites inside the protein.[7] The second mechanism focuses on the non-specific interactions between the anesthetic and the lipid membrane.[8]
In nuclear energy applications it is used in bubble chambers, probes, and in other areas where a high molecular weight and inert nature is a desirable quality.
Perxenates are used as oxidizing agents in analytical chemistry.
The isotope 133Xe is useful as a radioisotope.
Hyperpolarized MRI of the lungs and other tissues using 129Xe.[9]
Preferred fuel for Ion propulsion because of high atomic weight, ease of ionization, store as a liquid at near room temperature (but at high pressure) yet easily converts back into a gas to fuel the engine, inert nature makes it environmentally friendly and less corrosive to an ion engine than other fuels such as mercury or caesium. Europe's SMART-1 spacecraft utilized Xenon in its engines.[10]
Is used in protein crystallography. Applied at high pressure (~600 psi) to a protein crystal, xenon atoms bind in predominantly hydrophobic cavities, often creating a high quality, isomorphous, heavy-atom derivative..[11]
Xenon difluoride is used as an etchant for silicon, particularly in the production of microelectromechanical systems, or MEMS[12].

[edit] History
Xenon (from Greek ξένον meaning "strange one" or "stranger") was discovered in England by William Ramsay and Morris Travers on July 12, 1898, shortly after their discovery of the elements krypton and neon. They found it in the residue left over from evaporating components of liquid air.[13]


[edit] Occurrence
Xenon is a trace gas in Earth's atmosphere, occurring in one part in twenty million. The element is obtained commercially through extraction from the residues of liquefied air. This noble gas is naturally found in gases emitted from some mineral springs. Radioactive species of xenon, for example 133Xe and 135Xe are produced by neutron irradiation of fissionable material within nuclear reactors. Like the noble gas krypton, xenon can also be extracted by fractional distillation or liquefaction of liquid air and by selective adsorption on activated carbon.


[edit] Compounds

Xenon tetrafluorideXenon and the other noble gases had for a long time been considered to be completely chemically inert and not able to form compounds. However, in 1962 at the University of British Columbia, the first xenon compound, xenon hexafluoroplatinate, was synthesized by Neil Bartlett. Now, many compounds of xenon are known, including xenon difluoride, xenon tetrafluoride, xenon hexafluoride, xenon tetroxide, xenon hydrate, xenon deuterate, and sodium perxenate. A highly explosive compound xenon trioxide has also been made. There are at least 80 xenon compounds in which fluorine or oxygen is bonded to xenon. Some compounds of xenon are colored but most are colorless.

Recently at the University of Helsinki in Finland, a group of scientists (M. Räsänen et al.) prepared HXeH, HXeOH, and HXeCCH (xenon dihydride, xenon hydride-hydroxide, and hydroxenoacetylene). They are stable up to 40K.[14]


XeF4 crystals. 1962.
[edit] Isotopes
Main article: Isotopes of xenon
Naturally occurring xenon is made of seven stable and two slightly radioactive isotopes. Beyond these stable forms, there are 20 unstable isotopes that have been studied. 129Xe is produced by beta decay of 129I (half-life: 16 million years); 131Xe m, 133Xe, 133Xe m, and 135Xe are some of the fission products of both 235U and 239Pu, and therefore used as indicators of nuclear explosions.

The artificial isotope 135Xe is of considerable significance in the operation of nuclear fission reactors. 135Xe has a huge cross section for thermal neutrons, 2.65x106 barns, 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).

Relatively high concentrations of radioactive xenon isotopes are also found emanating from nuclear reactors due to the release of this fission gas from cracked fuel rods or fissioning of uranium in cooling water. The concentrations of these isotopes are still usually low compared to naturally occurring radioactive noble gases such as 222Rn.

Because xenon is a tracer for two parent isotopes, Xe isotope ratios in meteorites are a powerful tool for studying the formation of the solar system. The I-Xe method of dating gives the time elapsed between nucleosynthesis and the condensation of a solid object from the solar nebula. Xenon isotopes are also a powerful tool for understanding terrestrial differentiation. 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.[15]


[edit] Precautions
The gas can be safely kept in normal sealed glass containers at standard temperature and pressure. Xenon is non-toxic, but many of its compounds are toxic due to their strong oxidative properties.

The speed of sound in xenon is slower than that in air (due to the slower average speed of the heavy xenon atoms compared to nitrogen and oxygen molecules), so xenon lowers the resonant frequencies of the vocal tract when inhaled. This produces a characteristic lowered voice pitch, opposite the high-pitched voice caused by inhalation of helium. Like helium, xenon does not satisfy the body's need for oxygen and is a simple asphyxiant; 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 vs 131), is generally used in this stunt, although it too is an asphyxiant.

A myth exists that xenon is too heavy for the lungs to expel unassisted, and that after inhaling xenon, it is necessary to bend over completely at the waist to allow the excess gas to "spill" out of the body. In fact, the lungs mix gases very effectively and rapidly, such that xenon would be purged from the lungs within a breath or two. 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.


[edit] References
^ (2005) "Section 4, Properties of the Elements and Inorganic Compounds; Melting, boiling, triple, and critical temperatures of the elements", CRC Handbook of Chemistry and Physics, 85th edition, Boca Raton, Florida: CRC Press.
^ Los Alamos National Laboratory – Xenon
^ Thermophysical properties of neon, argon, krypton, and xenon / V. A. Rabinovich ... Theodore B. Selover, English-language edition ed, Washington [u.a.] Hemisphere Publ. Corp. [u.a.] , 1988. - XVIII (National standard reference data service of the USSR, You can now find Xenon at $60.00 per .077 pps
^ Caldwell, W. A.; Nguyen, J., Pfrommer, B., Louie, S., and Jeanloz, R. (1997). "Structure, bonding and geochemistry of xenon at high pressures". Science 277: 930-933.
^ Tonner PH. Xenon: one small step for anaesthesia... ? Current Opinion in Anaesthesiology. 2006 Aug;19(4):382-4.
^ Franks, John J. MD; Horn, Jean-Louis MD; Janicki, Piotr K. MD, PhD; Singh, Gurkeerat PhD. Halothane, Isoflurane, Xenon, and Nitrous Oxide Inhibit Calcium ATPase Pump Activity in Rat Brain Synaptic Plasma Membranes. Anesthesiology 1995, 82, 108-117.
^ Maria M. Lopez , Danuta Kosk-Kosicka. How Do Volatile Anesthetics Inhibit Ca2+-ATPases? Journal of Biological Chemistry 1995, 270, 28239-28245.
^ Thomas Heimburg and Andrew D. Jackson. The Thermodynamics of General Anesthesia. Biophysical Journal 2007, 92, 3159–3165. DOI:10.1529/biophysj.106.099754
^ Use of Xe in MRI
^ CNN Article regarding SMART-1 and Xenon
^ Xenon derivativation in protein crystllography at the Daresbury Synchrotron Radiation Source Laboratory, UK
^ Brazzle, J.D.; Dokmeci, M.R.; Mastrangelo, C.H.; Modeling and characterization of sacrificial polysilicon etching using vapor-phase xenon difluoride , 17th IEEE International Conference on Micro Electro Mechanical Systems (MEMS), 2004, pages 737-740.
^ Gagnon, Steve. It's Elemental - Xenon (English). Thomas Jefferson National Accelerator Facility. Retrieved on 16, 2007. Retrieved on June 2007.
^ See http://pubs.acs.org/cen/80th/noblegases.html in its paragraph starting "Many recent findings".
^ Boulos, M.S.; Manuel, O.K. (1971). "The xenon record of extinct radioactivities in the Earth.". Science 174: 1334-1336.

[edit] External links
Wikimedia Commons has media related to:
XenonLook up xenon in
Wiktionary, the free dictionary.WebElements.com – Xenon
Xenon as an anaesthetic
USGS Periodic Table - Xenon
Retrieved from "http://en.wikipedia.org/wiki/Xenon"
Categories: Chemical elements | Noble gases | Anesthetics | Xenon