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Cesium
Discovered in 1860 by R. Bunsen and G.R. Kirchoff at Heidelberg, Germany.
[Latin: caesius = sky blue]
French: cesium
German: Caesium
Italian: cesio
Spanish: cesio
Description: Caesium is
a soft, shiny, gold-colored metal which oxidises rapidly in air and reacts
explosively with water. It is obtained by the electrolysis of molten caesium
cyanide, and by other methods. Caesium and its salts are used comercially as
catalyst promoters, in special glasses, and in radiation monitoring equipment.
Materials properties
| Density: |
1843 kg/m-3 [293 K]; 1843 [liquid at m.p.] |
| Melting point: |
301.55 °K |
| Boiling point: |
951.6 °K |
| Molar volume: |
70.96 cm3 |
| Thermal conductivity: |
35.9 [300 K] Wm-1K-1 |
| Coefficient of linear thermal expansion: |
97 x 10-6 K-1 |
| Electrical resistivity: |
20 x 10-8 [293 K] Wm |
| Mass magnetic susceptibility: |
+2.8 x 10-9(s) kg-1m3 |
| Young's modulus: |
1.7 GPa |
| Rigidity modulus: |
0.65 GPa |
| Bulk modulus: |
n.a. |
| Poisson's ratio: |
0.295 GPa |
| Radii: |
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 |
| Issotope 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.
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| Level in humans |
|
| Blood: |
0.0038 mg dm-3 |
| Bone: |
0.013 - 0.052 p.p.m. |
| Liver: |
0.04 - 0.05 p.p.m. |
| Muscle: |
0.07 - 1.6 p.p.m. |
| Daily dietary intake : |
0.004 - 0.03 mg |
| Total mass of element in average [70 kg] person: |
c. 6 mg |
Crystal data
| Crystal structure, (cell dimentions / pm), space group |
b.c.c. (78 K) (a=614), Im3m High pressure forms: (a=598.4), Fm3m; (a=580.0), Fm3m |
| X-ray diffraction: mass absorption coefficients (µ/ρ)/cm2g-1: |
CuKα 318 MoKα 41.3 |
| Neutron scattering length, b/10-12cm: |
0.542 |
| Thermal neutron capture cross-section, σa/barns: |
29 |
Geological data
| Minerals: |
Few are known. |
| 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 ore: |
pollucite; caesium is also found in lepidolite |
| World production: |
c. 20 tonnes/year (caesium compounds) |
| Main mining areas: |
Bernic Lake (Manitoba, Canada), Bikita(Zimbabwe) and South-West Africa. |
| Reserves: |
c. 100 000 (60 000 at Bernic Lake) tonnes |
| Specimen: |
available as small ingots in sealed ampoules. Danger! |
| Abundances |
|
| Sun: |
< 80 (relative to H = 1 x 1023) |
| Earth's crust: |
3 p.p.m. |
| Seawater: |
3.0 x 10-4p.p.m. |
| Atlantic surface: |
n.a. |
| Atlantic deep: |
n.a. |
| Pacific surface: |
n.a. |
| Pacific deep: |
n.a. |
| Residence time: |
600 000 years |
| Classification: |
accumulating |
| Oxidation state: |
I |
Other sizes and specifications on request
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