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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.
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 |
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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 role: | No known biological role, but it may partly replace potassium |
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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 |
Minerals: | Few are known | |||
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Mineral | Formula | Density | Hardness | Crystal 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) |
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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 | |
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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