Caesium (Cs)

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Caesium 55Cs132.905


1860 von R. Bunsen und G.R. Kirchhoff in Heidelberg, Deutschland, entdeckt.

[Latin, caesius = himmelblau]

French: césium
English: Caesium/ Cesium
Italian: cesio
Spanish: cesio


Beschreibung: Weiches, glänzendes, goldfarbiges Metall, reagiert schnell mit Sauerstoff und explosiv mit Wasser. Verwendung für Katalysatoren als Promotor, in Spezialgläsern und in Strahlungswarnanlagen.

  


Further Materials properties

 

Crystal structure: (cell dimensions/pm), space group, 
b.c.c. (78 K) (a=614), Im3m
High pressure forms: (a= 598.4), Fm3m; (a=580.0), Fm3m
X-ray diffractions mass absorption coefficients: CuKa 318 (µ/r) / cm2g-1
MoKa 41.3 (µ/r) / cm2g-1
Neutron scattering length: 0.542 b/10-12 cm
Thermal neutron capture cross-section: 29 sa / barns
Density: 1873 kg/m-3 [293 K]; 1843[liquid at m.p.]
Melting point: 28.4°C / 301,55°K
Boiling point: 678.45°C / 951.6°K
Molar volume: 70.96 cm3
Thermal conductivity: 35.9 [300 K] W m-1K-1
Coefficient of linear thermal expansion: 97 x 10-6 K-1
Electrical resistivity: 20.0 x 10-8 [293 K] Ωm
Mass magnetic susceptibility: +2.8 x 10-8(s) kg-1m3
Young's modulus: 1.7 GPa
Rigidity modulus: 0.65 GPa
Bulk modulus: n.a.
Poisson's ratio: 0.295 GPa
Radi: Cs+ 165; atomic 265.4; covalent 235; van der Waals 262
Electronegativity: 0.79 (Pauling); 0.86 (Allred); 2.18 eV (absolute)
Effective nuclear charge: 2.20 (Slater); 6.36 (Clementi); 8.56 (Froese-Fischer)
Number of Isotopes (incl. nuclear isomers): 40
Isotope mass range: 114 -> 145

 

 


Biological data

 

Biological role: No known biological role, but it may partly replace potassium
Toxicity
Toxic intake: n.a. but regarded as fairly toxic
Lethal intake: LD50 (Cs2CO3, oral, rat) = 2333 mg Kg-1
Hazards: Although similar to potassium, caesium can have serious effects on the body if taken in excess. Rats fed Cs in place of K died after two weeks. 134Cs and 137Cs are dangerous radioactive pollutants which have escaped from nuclear reactors.
Level in humans  
Blood: 0.0038 mg dm-3
Bone: 0.013 - 0.052 ppm
Liver: 0.04 - 0.05 ppm
Muscle: 0.07 - 1.6 ppm
Daily dietary intake: 0.004 - 0.03 mg
Total mass of element in average
[70 kg] person:
c. 6 mg

 

Geological data

 

Minerals:Few are known
MineralFormulaDensityHardnessCrystal apperance
Cesium kupleskite  Cs3(Mn,Fe)7(Ti,Nb)2Si8O24.(OH,F)7  3.68  4  tric., dull gold-brown
Pollucite  (Cs,Na)2Al2Si4O12.nH2O  2.94  6.5  cub., col., vit.

Chief ores: pollucite; cesium is also found in lepidolite (see lithium)
World production: c. 20 (cesium compounds) tonnes/year
Main mining areas: Bernic Lake (Manitoba, Canada), Bikita (Zimbabwe) and South-West Africa
Reserves: c. 100 000 (60 000 at Bernic Lake)
Specimen: available as small ingots in sealed ampoules. Danger!

 

Abundances  
Sun: <80 (relative to H = 1 x 1012)
Earth's crust: 3 ppm
Seawater 3.0 x 10-4
Residence time: 600 000 years
Classification: accumulating
Oxidation state: I

  Source: Emsley, J. (1998) The Elements (3rd Edition)

Other sizes and specifications on request


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