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Title: Chemistry/Elements/Cesium - Wikipedia: Caesium Properties of the element, including its history, applications, and characteristics.

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Caesium

From Wikipedia, the free encyclopedia (Redirected from Cesium) Jump to: navigation, search 55xenon ← caesium → bariumRb↑Cs↓Fr

Periodic Table - Extended Periodic TableGeneralName, Symbol, Numbercaesium, Cs, 55Element categoryalkali metalsGroup, Period, Block1, 6, sAppearancesilvery gold

Standard atomic weight132.9054519(2) g·mol−1Electron configuration[Xe] 6s1Electrons per shell2, 8, 18, 18, 8, 1Physical propertiesPhasesolidDensity (near r.t.)1.93 g·cm−3Liquid density at m.p.1.843 g·cm−3Melting point301.59 K(28.44 °C, 83.19 °F)Boiling point944 K(671 °C, 1240 °F)Critical point1938 K, 9.4 MPaHeat of fusion2.09 kJ·mol−1Heat of vaporization63.9 kJ·mol−1Specific heat capacity(25 °C) 32.210 J·mol−1·K−1Vapor pressureP(Pa)1101001 k10 k100 kat T(K)418469534623750940Atomic propertiesCrystal structurebody centered cubicOxidation states1(strongly basic oxide)Electronegativity0.79 (Pauling scale)Ionization energies1st: 375.7 kJ/mol2nd: 2234.3 kJ/mol3rd: 3400 kJ/molAtomic radius260 pmAtomic radius (calc.)298 pmCovalent radius225 pmMiscellaneousMagnetic orderingno dataElectrical resistivity(20 °C) 205 n Ω·mThermal conductivity(300 K) 35.9 W·m−1·K−1Thermal expansion(25 °C) 97 µm·m−1·K−1Young's modulus1.7 GPaBulk modulus1.6 GPaMohs hardness0.2Brinell hardness0.14 MPaCAS registry number7440-46-2Most-stable isotopesMain article: Isotopes of caesiumisoNAhalf-lifeDMDE (MeV)DP133Cs100%133Cs is stable with 78 neutrons134Cssyn65.159 Ms(2.0648y)ε1.229134Xeβ-2.059134Ba135Cstrace73 Ts(2,300,000y)β-0.269135Ba137Cssyn948.9 Ms(30.07y)β-1.176137BaReferencesCaesium or cesium (pronounced /ˈsiːziəm/) is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C (83 °F), which makes it one of only five metals that are liquid at or near room temperature.[1] Caesium is most notably used in atomic clocks.Caesium is the international spelling standardized by the IUPAC, but in North American English, the spelling cesium is more common.[2]

1 Characteristics2 Applications3 History4 Occurrence5 Isotopes6 Precautions7 See also8 References9 External links//

[edit] Characteristics

High purity caesium metal.The emission spectrum of caesium has two bright lines in the blue area of the spectrum along with several other lines in the red, yellow, and green areas. This metal is silvery gold in color and is both soft and ductile. Caesium has the lowest ionization potential of the chemical elements. Caesium is the least abundant of the five non-radioactive alkali metals (francium is the least common alkali metal, but since it is highly radioactive with an estimated 30 grams in the entire Earth's crust at one time,[3] its abundance can be considered as zero in practical terms).Along with gallium, francium, rubidium, and mercury, caesium is among the only metals that are liquid at or near room temperature. Caesium reacts explosively in cold water and also reacts with ice at temperatures above −116 °C (−177 °F, 157 K).Caesium hydroxide (CsOH) is a very strong base and will rapidly etch the surface of glass. CsOH is often stated to be the "strongest base", but in fact many compounds such as n-butyllithium and sodium amide are stronger.

[edit] Applications

Probably the most widespread use of caesium today is in caesium formate-based drilling fluids for the oil industry. The high density of the caesium formate brine (up to 2.3 sg), coupled with the relatively benign nature of 133Cs, reduces the requirement for toxic high-density suspended solids in the drilling fluid, which is a significant technological, engineering and environmental advantage.[4][5]Caesium is also used in atomic clocks, which are accurate to seconds over many thousands of years. Since 1967, the International System of Measurements has based its unit of time, the second, on the properties of caesium. The International System of Units (SI) defines the second as 9,192,631,770 cycles of the radiation, which corresponds to the transition between two hyperfine energy levels of the ground state of the 133Cs atom.134Cs has been used in hydrology as a measure of caesium output by the nuclear power industry. This isotope is used because, while it is less prevalent than either 133Cs or 137Cs, 134Cs can be produced solely by nuclear reactions. 135Cs has also been used in this function.Like other elements of group 1, caesium has a great affinity for oxygen and is used as a "getter" in vacuum tubes.This metal is also used in photoelectric cells due to its ready emission of electrons.Caesium was used as a propellant in early ion engines. It used a method of ionization to strip the outer electron from the propellant by simple contact with tungsten. Caesium use as a propellant was discontinued when Hughes Research Laboratory conducted a study finding xenon gas as a suitable replacement.Caesium is used as a catalyst in the hydrogenation of certain organic compounds.Radioactive isotopes of caesium are used in the medical field to treat certain types of cancer.Caesium fluoride is widely used in organic chemistry as a base and as a source of anhydrous fluoride ion.Caesium vapor is used in many common magnetometers.Because of their high density, caesium chloride solutions are commonly used in molecular biology for density gradient ultracentrifugation, primarily for the isolation of viral particles, subcellular organelles and fractions, and nucleic acids from biological samples.Caesium nitrate is used as an oxidizer to burn silicon in infrared flares[6] such as the LUU-19 flare,[7] because it emits much of its light in the near infrared spectrum.Caesium-137 is an extremely common radioisotope used as a gamma-emitter in industrial applications such as:moisture density gaugesleveling gaugesthickness gaugeswell-logging devices which are used to measure the electron density, which is analogous to the bulk density, of the rock formations.Caesium is also used as an internal standard in spectrophotometry.Caesium has been used to reduce the radar signature of exhaust plumes in military aircraft.

[edit] History

Caesium (Latin caesius meaning "blueish grey")[8][9] was spectroscopically discovered by Robert Bunsen and Gustav Kirchhoff in 1860 in mineral water from Dürkheim, Germany. The residues of 44,000 liters of mineral water yielded several grams of caesium salt for further analysis. Its identification was based upon the bright blue lines in its spectrum and it was the first element discovered by spectrum analysis.[10] The first caesium metal was produced in 1882 by electrolysis of caesium chloride by Carl Setterberg. Setterberg received his PhD from Kekule and Bunsen for this work. Historically, the most important use for caesium has been in research and development, primarily in chemical and electrical applications.

[edit] Occurrence

Pollucite, a caesium mineral.An alkali metal, caesium occurs in lepidolite, pollucite (hydrated silicate of aluminium and caesium) and within other sources. One of the world's most significant and rich sources of this metal is at Bernic Lake in Manitoba. The deposits there are estimated to contain 300,000 metric tons of pollucite at an average of 20% caesium.It can be isolated by electrolysis of fused caesium cyanide and in a number of other ways. Exceptionally pure and gas-free caesium can be made by the thermal decomposition of caesium azide. The primary compounds of caesium are caesium chloride and its nitrate. The price of caesium metal in 1997 was about US$30 per gram, but its compounds are much cheaper.See also Caesium minerals.

[edit] Isotopes

Main article: isotopes of caesiumCaesium has at least 39 known isotopes, which is more than any other element except francium. The atomic masses of these isotopes range from 112 to 151. Even though this element has a large number of isotopes, it has only one naturally occurring stable isotope, 133Cs. Most of the other isotopes have half-lives from a few days to fractions of a second. The radiogenic isotope 137Cs has been used in hydrologic studies, analogous to the use of 3H. 137Cs is produced from the detonation of nuclear weapons and is produced in nuclear power plants, and was released to the atmosphere most notably from the 1986 Chernobyl meltdown. This isotope (137Cs) is one of the numerous products of fission, directly issued from the fission of uranium.

High purity caesium-133 (preserved under argon)Beginning in 1945 with the commencement of nuclear testing, 137Cs was released into the atmosphere where it is not absorbed readily into solution and is returned to the surface of the earth as a component of radioactive fallout. Once 137Cs enters the ground water, it is deposited on soil surfaces and removed from the landscape primarily by particle transport. As a result, the input function of these isotopes cannot be estimated as a function of time. Caesium-137 has a half-life of 30.17 years. It decomposes to barium-137m (a short-lived product of decay) then to a form of nonradioactive barium.

[edit] Precautions

All alkali metals are highly reactive. Caesium, being one of the heavier alkali metals, is also one of the most reactive and is highly explosive when it comes in contact with water. The hydrogen gas produced by the reaction is heated by the thermal energy released at the same time, causing ignition and a violent explosion (the same as all alkali metals) - but caesium is so reactive that this explosive reaction can even be triggered by cold water or ice.Caesium is highly pyrophoric and ignites spontaneously in air to form caesium hydroxide and various oxides. Caesium hydroxide is an extremely strong base, and can etch glass.Caesium compounds are rarely encountered by most persons. All caesium compounds should be regarded as mildly toxic because of its chemical similarity to potassium. Large amounts cause hyperirritability and spasms, but such amounts would not ordinarily be encountered in natural sources, so Cs is not a major chemical environmental pollutant. Rats fed caesium in place of potassium in their diet die,[citation needed] so this element cannot replace potassium in function.The isotopes 134Cs and 137Cs (present in the biosphere in small amounts as a result of radiation leaks) represent a radioactivity burden which varies depending on location. Radiocaesium does not accumulate in the body as effectively as many other fission products (such as radioiodine and radiostrontium), which are actively accumulated by the body.[citation needed]

[edit] See also

v • d • eAlkali metals LithiumLiAtomic Number: 3Atomic Weight: 6.941Melting Point: 453.69Boiling Point: 1615Electronegativity: 0.98SodiumNaAtomic Number: 11Atomic Weight: 22.990Melting Point: 370.87Boiling Point: 1156Electronegativity: 0.96PotassiumKAtomic Number: 19Atomic Weight: 39.098Melting Point: 336.58Boiling Point: 1032Electronegativity: 0.82RubidiumRbAtomic Number: 37Atomic Weight: 85.468Melting Point: 312.46Boiling Point: 961Electronegativity: 0.82CaesiumCsAtomic Number: 55Atomic Weight: 132.905Melting Point: 301.59Boiling Point: 944Electronegativity: 0.79FranciumFrAtomic Number: 87Atomic Weight: (223)Melting Point: ?295Boiling Point: ?950Electronegativity: 0.7Cs-137Goiânia accident, a major radioactive contamination incident involving a small rod of caesium chloride.Caesium compoundsDirty bomb

[edit] References

Wikisource has the text of the 1911 Encyclopædia Britannica article Caesium.^ Along with rubidium (39 °C [102 °F]), francium (27 °C [81 °F]), mercury (−39 °C [−38 °F]), and gallium (30 °C [86 °F]).Bromine is also liquid at room temperature (-7.2 °C, 19 °F) but it is not a metal, but a halogen.^ IUPAC Periodic Table of the Elements^ Adloff, Jean-Pierre; George B. Kauffman (09/23 2005). "Francium (Atomic Number 87), the Last Discovered Natural Element". The Chemical Educator 10 (5). doi:10.1333/s00897050956a, http://chemeducator.org/sbibs/s0010005/spapers/1050387gk.htm. Retrieved on 16 May 2006. ^ Drilling and Completing Difficult HP/HT Wells With the Aid of Cesium Formate Brines-A Performance Review^ Overview: Cesium Formate Fluids^ United States Patent 6230628: Infrared illumination compositions and articles containing the same^ LUU-19 Flare^ Bunsen quotes Aulus Gellius Noctes Atticae II, 26 by Nigidius Figulus: Nostris autem veteribus caesia dicts est quae Graecis, ut Nigidus ait, de colore coeli quasi coelia.^ Oxford English Dictionary, 2nd Edition^ G. Kirchhoff, R. Bunsen (1861). "Chemische Analyse durch Spectralbeobachtungen". Annalen der Physik und Chemie 189 (7): 337–381. doi:10.1002/andp.18611890702. Los Alamos National Laboratory - CesiumDaniel A. Steck. "Cesium D Line Data". Los Alamos National Laboratory (technical report LA-UR-03-7943).

[edit] External links

Wikimedia Commons has media related to: Caesium

Look up caesium inWiktionary, the free dictionary.WebElements.com – CaesiumHumor site dedicated to caesiumv • d • ePeriodic tableH HeLiBe BCNOFNeNaMg AlSiPSClArKCa ScTiVCrMnFeCoNiCuZnGaGeAsSeBrKrRbSr YZrNbMoTcRuRhPdAgCdInSnSbTeIXeCsBaLaCePrNdPmSmEuGdTbDyHoErTmYbLuHfTaWReOsIrPtAuHgTlPbBiPoAtRnFrRaAcThPaUNpPuAmCmBkCfEsFmMdNoLrRfDbSgBhHsMtDsRgUubUutUuqUupUuhUusUuoUueUbn Alkali metalsAlkaline earth metalsLanthanoidsActinoidsTransition metalsOther metalsMetalloidsOther nonmetalsHalogensNoble gasesRetrieved from "http://en.wikipedia.org/wiki/Caesium" Categories: Chemical elements | Alkali metals | CaesiumHidden categories: All articles with unsourced statements | Articles with unsourced statements since June 2008 Views Article Discussion Edit this page History Personal tools Log in / create account if (window.isMSIE55) fixalpha(); Navigation Main page Contents Featured content Current events Random article Search Interaction About Wikipedia Community portal Recent changes Contact Wikipedia Donate to Wikipedia Help Toolbox What links here Related changesUpload fileSpecial pages Printable version Permanent linkCite this page Languages Afrikaans العربية বাংলা Беларуская Bosanski Български Català Česky Corsu Cymraeg Dansk Deutsch Eesti Ελληνικά Español Esperanto Euskara فارسی Français Furlan Gaeilge Gaelg Galego 한국어 Հայերեն Hrvatski Ido Bahasa Indonesia Íslenska Italiano עברית Kiswahili Kreyòl ayisyen Kurdî / كوردی Latina Latviešu Lëtzebuergesch Lietuvių Lojban Magyar Македонски മലയാളം मराठी Nederlands 日本語 ‪Norsk (bokmål)‬ ‪Norsk (nynorsk)‬ Occitan Polski Português Română Runa Simi Русский Seeltersk Sicilianu Simple English Slovenčina Slovenščina Српски / Srpski Srpskohrvatski / Српскохрватски Suomi Svenska தமிழ் ไทย Tiếng Việt Türkçe Українська اردو Walon 粵語中文 ಕನ್ನಡ Powered by MediaWiki

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