Cesium

Cesium - Cs

CAS: 7440-46-2
Description: Soft, light, silvery-white metal
Classification: Alkali Metal
Date of Discovery: 1860
Discoverer: Fustov Kirchoff
Name Origin: Latin caesius, "sky blue"
Alternative Spelling: Caesium

Atomic Number: 55
Number of Neutrons: 78
Atomic Mass: 132.90543(5) amu
Melting Point: 28.44 ± 0.01 °C
Boiling Point: 671 °C
Density (293 K): 1.873 g/cm³
Atomic volume: 71.07 cm³/mol
Electrical resistivity: 0.0489 10^-6/cm

Thermal conductivity: 0.359 W/cmK
Enthalpy of atomization: 78.24 kJ/mol
Enthalpy of vaporization: 67.740 kJ/mol
Enthalpy of fusion: 2.092 kJ/mol
Specific heat capacity: 0.24 J/gK

Energy levels: 2-8-18-18-8-1
Electron configuration: [Xe]6s¹
Crystal Structure: Cubic body centered
Atomic radius: 3.34 Å
Covalent radius: 2.35 Å
Oxidation States: +1
Electronegativity, Pauling: 0.79
Electron affinity: 0.471626 eV
First ionization energy: 3.894 eV
2nd ionization energy: 25.10 eV
3rd ionization energy:
Polarizability: 59.6 10^-24cm³

Isotope	Natural Abundance	Atomic Mass	Half-life	Decay Mode	Spin
¹¹²Cs	111.9503	0.5 ms	p
¹¹³Cs	112.9445	17 µs	p
¹¹⁴Cs	113.9408	0.58 s	⁺, EC	1+
¹¹⁵Cs	144.9359	1.4 s	⁺, EC
^116mCs	0.7 s	⁺, EC
¹¹⁶Cs	115.9330	3.8 s	⁺, EC
^117mCs	6.5 s	⁺, EC
¹¹⁷Cs	116.9286	8.4 s	⁺, EC
^118mCs	17 s	⁺, EC
¹¹⁸Cs	117.92654	14 s	⁺, EC	2
^119mCs	28 s	3/2
¹¹⁹Cs	118.92234	38 s	⁺, EC	9/2+
^120mCs	60 s	⁺, EC
¹²⁰Cs	119.92066	64 s	⁺, EC	2+
^121mCs	2.0 m	IT; ⁺	(9/2+)
¹²¹Cs	120.91718	⁺	3/2+
^122m2Cs	4.4 m	⁺, EC	8-
^122m1Cs	0.36 s	IT
¹²²Cs	121.91614	21 s	⁺, EC	(1+)
^123mCs	1.6 s	IT	11/2-
¹²³Cs	122.91299	5.87 m	⁺; EC	1/2+
^124mCs	6.3 s	IT	7+
¹²⁴Cs	123.91225	30 s	⁺; EC	1+
¹²⁵Cs	124.90972	45 m	⁺; EC	1/2+
¹²⁶Cs	125.90945	1.64 m	⁺; EC	1+
¹²⁷Cs	126.90741	6.2 h	⁺; EC	1/2+
¹²⁸Cs	127.90775	3.62 m	⁺; EC	1+
¹²⁹Cs	128.90606	1.336 d	EC	1/2+
^130mCs	3.5 m	IT, ⁺, EC	5-
¹³⁰Cs	129.90671	29.21	⁺; EC	1+
¹³¹Cs	130.90546	9.69 d	EC	5/2+
¹³²Cs	131.906430	6.48 d	EC; ⁺; ^-	2-
¹³³Cs	100.	132.905447	Stable	7/2+
^134mCs	2.91 h	IT	8-
¹³⁴Cs	133.906714	2.065 y	^-; EC	4+
^135mCs	53 m	IT	19/2-
¹³⁵Cs	134.905972	2.3 x 10⁶ y	^-	7/2+
^136mCs	19 s	IT	8
¹³⁶Cs	135.907307	13.16 d	^-	5+
¹³⁷Cs	136.907085	30.2 y	^-	7/2+
^138mCs	2.9 m	IT; ^-	6-
¹³⁸Cs	137.91101	32.2 m-	^-	3-
¹³⁹Cs	138.913359	9.3 m	^-	7/2+
¹⁴⁰Cs	139.91727	1.06 m	^-	1-
¹⁴¹Cs	140.92005	24.9 s	^-	7/2+
¹⁴²Cs	141.92430	1.8 s	^-
¹⁴³Cs	142.92732	1.78 s	^-	(3/2+)
¹⁴⁴Cs	143.93203	1.01 s	^-	1
¹⁴⁵Cs	144.93541	0.59 s	^-	3/2+
¹⁴⁶Cs	145.94024	0.322 s	^-	2-
¹⁴⁷Cs	146.9439	0.227 s	^-, (n)
¹⁴⁸Cs	147.9490	0.15 s	^-, (n)
Cesium was discovered spectroscopically by Bunsen and Kirchhoff in 1860 in mineral water from Durkheim. Cesium, an alkali metal, occurs in lepidolite, pollucite [(Cs₄Al₄Si₉O₂₆).H₂O], and in other sources. One of the world's richest sources of cesium is located at Bemic Lake, Manitoba. The deposits are estimated to contain 300,000 tons of pollucite, averaging 20% cesium. It can be isolated by electrolysis of the fused cyanide and by a number of other methods. Very pure, gas-free cesium can be prepared by thermal decomposition of cesium azide. The metal is characterized by a spectrum containing two bright lines in the blue along with several others in the red, yellow, and green. It is silvery white, soft, and ductile. It is the most electropositive and most alkaline element. Cesium, gallium, and mercury are the only three metals that are liquid at room temperature. Cesium reacts explosively with cold water, and reacts with ice at temperatures above -116 deg C. Cesium hydroxide, the strongest base known, attacks glass. Because of its great affinity for oxygen the metal is used as a "getter" in electron tubes. It is also used in photoelectric cells, as well as a catalyst in the hydrogenation of certain organic compounds. The metal has recently found application in ion propulsion systems. Cesium is used in atomic clocks, which are accurate to 5 s in 300 years. Its chief compounds are the chloride and the nitrate. Cesium has 52 isotopes and isomers with masses ranging from 112 to 148. LINKS: AMM Online - Cesium Profile Cesium Atomic Clocks Cesium atoms for optical computers Minerals Containing Cesium The NIST Cesium Clock Return Sources for the information on this website include: Lide, David R., ed. CRC Handbook of Chemistry and Physics, 78th Ed., 1997-1998.

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