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Caesium History | Isotopes and compounds | References | Navigation menuedit"Atomic weights of the elements 2013 (IUPAC Technical Report)"10.1515/pac-2015-030510.1002/anie.197905871Handbook of Chemistry and Physics"NIST Radionuclide Half-Life Measurements""Mineral Commodity Profile: Cesium"10.1002/andp.18611890702e

Alkali metalsChemical elements


chemical elementatomic numberperiodic tablealkalimetalmeltingreactivedangerousexplodesalkali metalsmineral oilEarthpotassiumGustav Robert KirchhoffRobert Wilhelm Bunsenmineral waterBad Dürkheimcalciumstrontiummagnesiumlithiumspectrumblueisotoperadioactiveatomic clockssecondnuclear fissiongamma raycompoundschemical elementsdensity












Caesium




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Caesium,  55Cs
Some pale gold metal, with a liquid-like texture and lustre, sealed in a glass ampoule
General properties
Pronunciation
/ˈsziəm/(SEE-zee-əm)
Alternative namecesium (US, informal)
Appearancepale gold

Standard atomic weight.mw-parser-output .noboldfont-weight:normal
(Ar, standard)

132.90545196(6)[1]
Caesium in the periodic table



































































































































Hydrogen


Helium

Lithium

Beryllium


Boron

Carbon

Nitrogen

Oxygen

Fluorine

Neon

Sodium

Magnesium


Aluminium

Silicon

Phosphorus

Sulfur

Chlorine

Argon

Potassium

Calcium

Scandium


Titanium

Vanadium

Chromium

Manganese

Iron

Cobalt

Nickel

Copper

Zinc

Gallium

Germanium

Arsenic

Selenium

Bromine

Krypton

Rubidium

Strontium

Yttrium



Zirconium

Niobium

Molybdenum

Technetium

Ruthenium

Rhodium

Palladium

Silver

Cadmium

Indium

Tin

Antimony

Tellurium

Iodine

Xenon

Caesium

Barium

Lanthanum

Cerium

Praseodymium

Neodymium

Promethium

Samarium

Europium

Gadolinium

Terbium

Dysprosium

Holmium

Erbium

Thulium

Ytterbium

Lutetium

Hafnium

Tantalum

Tungsten

Rhenium

Osmium

Iridium

Platinum

Gold

Mercury (element)

Thallium

Lead

Bismuth

Polonium

Astatine

Radon

Francium

Radium

Actinium

Thorium

Protactinium

Uranium

Neptunium

Plutonium

Americium

Curium

Berkelium

Californium

Einsteinium

Fermium

Mendelevium

Nobelium

Lawrencium

Rutherfordium

Dubnium

Seaborgium

Bohrium

Hassium

Meitnerium

Darmstadtium

Roentgenium

Copernicium

Nihonium

Flerovium

Moscovium

Livermorium

Tennessine

Oganesson


Rb

Cs

Fr

xenon ← caesium → barium
Atomic number (Z)55
Groupgroup 1 (alkali metals)
Period
period 6
Block
s-block
Element category
  alkali metal
Electron configuration[Xe] 6s1
Electrons per shell
2, 8, 18, 18, 8, 1
Physical properties

Phase
at STP
solid
Melting point301.7 K ​(28.5 °C, ​83.3 °F)
Boiling point944 K ​(671 °C, ​1240 °F)

Density (near r.t.)
1.93 g/cm3
when liquid (at m.p.)1.843 g/cm3
Critical point1938 K, 9.4 MPa[2]
Heat of fusion2.09 kJ/mol
Heat of vaporization63.9 kJ/mol
Molar heat capacity32.210 J/(mol·K)

Vapor pressure
















P (Pa)
1
10
100
1 k
10 k
100 k
at T (K)
418
469
534
623
750
940

Atomic properties
Oxidation states−1, +1[3] (a strongly basic oxide)
ElectronegativityPauling scale: 0.79
Ionization energies
  • 1st: 375.7 kJ/mol

  • 2nd: 2234.3 kJ/mol

  • 3rd: 3400 kJ/mol


Atomic radiusempirical: 265 pm
Covalent radius244±11 pm
Van der Waals radius343 pm

Color lines in a spectral range

Spectral lines of caesium
Other properties
Natural occurrenceprimordial
Crystal structure ​body-centered cubic (bcc)
Bodycentredcubic crystal structure for caesium

Thermal expansion97 µm/(m·K) (at 25 °C)
Thermal conductivity35.9 W/(m·K)
Electrical resistivity205 nΩ·m (at 20 °C)
Magnetic ordering
paramagnetic[4]
Young's modulus1.7 GPa
Bulk modulus1.6 GPa
Mohs hardness0.2
Brinell hardness0.14 MPa
CAS Number7440-46-2
History
Namingfrom Latin caesius, sky blue, for its spectral colours
Discovery
Robert Bunsen and Gustav Kirchhoff (1860)
First isolation
Carl Setterberg (1882)
Main isotopes of caesium



























Iso­tope

Abun­dance

Half-life
(t1/2)

Decay mode

Pro­duct

133Cs
100%

stable

134Cs

syn
2.0648 y

ε

134Xe

β

134Ba

135Cs

trace
2.3×106 y
β
135Ba

137Cs
syn
30.17 y[5]β
137Ba

| references

Caesium (or cesium) is the chemical element with the atomic number 55 on the periodic table. Its symbol is Cs.


Caesium is an alkali metal. Its melting point is low (28 °C). It is extremely reactive. Because of its high reactivity, it is a dangerous chemical. It may set itself on fire (ignite) in air. It explodes on contact with water. It reacts more violently than the other alkali metals with water. Because of this, caesium is stored in mineral oil.[6]


Caesium is a rare element. Since there is little caesium on the Earth, it is rather expensive. The human body does not need caesium. In large amounts, it is mildly poisonous because it is close to potassium, which the body does need.



History |


Caesium was first described in 1861, by Gustav Robert Kirchhoff and Robert Wilhelm Bunsen. They were testing mineral water, from Bad Dürkheim. After they separated calcium, strontium, magnesium and lithium, they saw two lines in the "blue" range of the spectrum. Because of these lines, they concluded that in addition to the elements already found, there must be another unknown substance in the mineral water. They named this substance caesium, after the color blue.[7]



Isotopes and compounds |


Caesium has at least 39 known isotopes ranging in atomic mass from 112 to 151. Only one of these, 133Cs, is stable. Therefore, the naturally-occurring isotope of caesium is 133Cs, which is not radioactive. 133Cs is used in atomic clocks, its vibration frequency used to define the length of the second. Another isotope, 137Cs is not made naturally but is made after nuclear fission has been done. It is very radioactive and used as an industrial gamma ray source.


Caesium forms compounds with many other chemical elements. Caesium formate is used in oil drilling because of its high density.



References |




  1. Meija, J.; Coplen, T. B.; Berglund, M.; Brand, W.A.; De Bièvre, P.; Gröning, M.; Holden, N.E.; Irrgeher, J. et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry 88 (3): 265-91. doi:10.1515/pac-2015-0305. https://www.degruyter.com/downloadpdf/j/pac.2016.88.issue-3/pac-2015-0305/pac-2015-0305.xml. 


  2. Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.121. ISBN 1439855110..mw-parser-output cite.citationfont-style:inherit.mw-parser-output .citation qquotes:"""""""'""'".mw-parser-output .citation .cs1-lock-free abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .citation .cs1-lock-limited a,.mw-parser-output .citation .cs1-lock-registration abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .citation .cs1-lock-subscription abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registrationcolor:#555.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration spanborder-bottom:1px dotted;cursor:help.mw-parser-output .cs1-ws-icon abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Wikisource-logo.svg/12px-Wikisource-logo.svg.png")no-repeat;background-position:right .1em center.mw-parser-output code.cs1-codecolor:inherit;background:inherit;border:inherit;padding:inherit.mw-parser-output .cs1-hidden-errordisplay:none;font-size:100%.mw-parser-output .cs1-visible-errorfont-size:100%.mw-parser-output .cs1-maintdisplay:none;color:#33aa33;margin-left:0.3em.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-formatfont-size:95%.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-leftpadding-left:0.2em.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-rightpadding-right:0.2em


  3. 3.03.1 Dye, J. L. (1979). "Compounds of Alkali Metal Anions". Angewandte Chemie International Edition 18 (8): 587–598. doi:10.1002/anie.197905871. 


  4. "Magnetic susceptibility of the elements and inorganic compounds". Handbook of Chemistry and Physics (PDF) (87th ed.). CRC press. ISBN 0-8493-0487-3. Retrieved 2010-09-26.


  5. "NIST Radionuclide Half-Life Measurements". NIST. Retrieved 2011-03-13.


  6. William C. Butterman et al 2004. "Mineral Commodity Profile: Cesium" (PDF). United States Geological Survey. Retrieved 2009-12-27.


  7. G. Kirchhoff, R. Bunsen: Chemische Analyse durch Spectralbeobachtungen. In: Annalen der Physik und Chemie. 1861, 189, 7, S. 337–381 (doi:10.1002/andp.18611890702).











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