Element Cesium

Cesium ElementCesium (Caesium) is a soft, silvery-gold alkali metal with a melting point of 28 °C (82 °F). Cesium is used in various industries, from the oil industry as cesium formate in drilling fluid, atomic clocks, centrifugation fluids, and cesium vapor thermionic generators, which convert heat energy to electrical energy.
Cesium is a naturally occurring element found combined with other elements in rocks, soil, and dust in low amounts. Naturally occurring cesium is not radioactive and is referred to as stable cesium.
Cesium, the most electropositive and least abundant of the five naturally occurring alkali metals, was discovered spectroscopically in 1860. The first cesium metal was produced in 1881. Because cesium is not mined domestically, the United States is completely dependent on imports. Historically, the most important use for cesium has been in research and development, primarily in chemical and electrical applications.

Names and Identifiers

Chemical Formula:Cs
Molecular Weight:132.90500 g/mol
EC Number :231-155-4
MDL Number:MFCD00134037
Color:silvery gold/yellow
Other Names:Caesium
PubChem CID:5354618
IUPAC Name:Cesium
Canonical SMILES:[Cs]
ICSC Number:n/a

Physical & Chemical Properties

Boiling Point:944 K ​(671 °C, ​1240 °F)
Melting Point:312.45 K (39.30 °C, 102.74 °F)
Molecular Formula:Cs
Flash Point:n/a
Exact Mass:132.90500
Symbol:Globally Harmonized System of ClassificationGlobally Harmonized System of Classification
Signal Word:Danger
Hazard Statements:H260-H314
Precautionary Statements:P223-P231 + P232-P280-P305 + P351 + P338-P370 + P378-P422
Hazard Codes:F:Highlyflammable; C:Corrosive;
Risk Phrases:R14/15;R34
Safety Phrases:S26-S45-S43-S36/37/39-S16-S8
RIDADR:UN 3264 8/PG 3
WGK Germany:3
Packaging Group:I
Hazard Class:4.3

Caesium (55Cs) has 40 known isotopes, making it, along with barium and mercury, one of the elements with the most isotopes.[3] The atomic masses of these isotopes range from 112 to 151. Only one isotope, 133Cs, is stable. The longest-lived radioisotopes are 135Cs with a half-life of 2.3 million years, 137Cs with a half-life of 30.1671 years and 134Cs with a half-life of 2.0652 years. All other isotopes have half-lives less than 2 weeks, most under an hour.

Naturally occurring isotopes

IsotopeMass/DaNatural abundance (atom %)Nuclear spin (I)Magnetic moment (μ/μN)
133Cs132.905429 (7)1007/22.582024

Radiosotope data

IsotopeMass/DaHalf-lifeMode of decayNuclear spinNuclear magnetic moment
129Cs128.906061.336 dEC to 129Xe1/21.49
130Cs129.9067129.21 mEC to 130Xe; β to 130Ba11.46
131Cs130.905469.69 dEC to 131Xe5/23.54
132Cs131.9064306.48 dEC to 132Xe; β to 132Ba22.22
134Cs133.9067142.065 yEC to 134Xe; β to 134Ba42.994
135Cs134.9059722.3 x 106 yβ to 135Ba7/22.732
136Cs135.90730713.16 dβ to 136Ba53.71
137Cs136.90708530.2 yβ to 137Ba7/22.84

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