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Selenium (Se)
We are a leading manufacturer and supplier of research materials
Selenium 34Se78.96
Discovered in 1817 by J.J. Berzelius at Stockholm, Sweden.
[Greek, selene = moon]
French: sélenium
German: Selen
Italian: selenio
Spanish: selenio
Description: Selenium is obtained in either a silvery metallic form (grey Se) or a red amorphous powder, which is less stable. Selenium burns in air, is unaffected by water, but dissolves in concentrated HNO3 and alkalis. It is used in photoelectric cells, photocopiers, solar cells and semiconductors.
Further Materials properties
| Crystal structure: |
(cell dimensions/pm), space group, |
|---|---|
| X-ray diffractions mass absorption coefficients: | CuKa 91.4 (µ/r) / cm2g-1 MoKa 74.7 (µ/r) / cm2g-1 |
| Neutron scattering length: | 0.797 b/10-12 cm |
| Thermal neutron capture cross-section: | 11.7 sa / barns |
| Density: | 4790 (grey) kg/m-3 [293 K]; 3987 [liquid at m.p.] |
| Melting point: | 216.85 °C / 490 °K |
| Boiling point: | 684.95°C / 958.1°K |
| Molar volume: | 16.48 cm3 |
| Thermal conductivity: | 2.04 (α) [300 K] W m-1K-1 |
| Coefficient of linear thermal expansion: | 36.9 x 10-6 K-1 |
| Electrical resistivity: | 0.01 [293 K] Ωm |
| Mass magnetic susceptibility: | -4.0 x 10-9(s) kg-1m3 |
| Radi: | Se4+ 69; Se2- 191; atomic 215; covalent 117: van der Waals 200 |
| Electronegativity: | 2.55 (Pauling); 2.48 (Allred); 5.89 eV (absolute) |
| Effective nuclear charge: | 6.95 (Slater); 8.29 (Clementi); 9.96 (Froese-Fischer) |
| Number of Isotopes (incl. nuclear isomers): | 26 |
| Isotope mass range: | 69 -> 89 |
Biological data
| Biological role: | Essential to some species, including humans, although only in tiny amounts. Selenium acts to stimulate the metabolism. |
|---|---|
| Toxicity | |
| Toxic intake: | human, Se metal = c. 10 - 35 mg |
| Lethal intake: | LD50 (Se metal, oral, rat) = 6700 mg Kg-1. A dose of 5 mg per day can be lethal for many humans. LD50 (H2SeO3, intravenous, mouse) = 11 mg Kg-1 |
| Hazards: | Selenium compounds are toxic by inhalation and intravenous routes. They are also considered to be experimental carcinogens and teratogens. |
| Level in humans | |
| Blood: | 0.171 mg dm-3 |
| Bone: | 1 - 9 ppm |
| Liver: | 0.35 - 2.4 ppm |
| Muscle: | 0.42 - 1.9 ppm |
| Daily dietary intake: | 0.006 - 0.2 mg |
| Total mass of element in average [70 kg] person: |
c. 15 mg (wide range possible, 10-65 mg) |
Geological data
| Minerals: | Native selenium is occasionally found; several minerals are known, but all are very rare and generally they occur together with sulfides of metals such as copper, zinc and lead. | |||
|---|---|---|---|---|
| Mineral | Formula | Density | Hardness | Crystal apperance |
| Clausthalite | PbSe | 7.8 | 2.5 - 3 | cub., met. grey |
| Crooksite | Cu7TlSe4 | 6.9 | 2.5 - 3 | tetragonal, met., grey |
Note: the mineral called selenite is in fact calcium sulfate
| Chief ores: | by-product of electro-refining of copper. |
|---|---|
| World production: | 1 600 tonnes/year |
| Main mining areas: | Canada, USA, Bolivia and Russia. |
| Reserves: | n.a. |
| Specimen: | available as powder or pellets. Care! |
| Abundances | |
|---|---|
| Sun: | n.a. (relative to H = 1 x 1012) |
| Earth's crust: | 0.05 ppm |
| Seawater | |
| Atlantic surface: | 0.46 x 10-7 ppm |
| Atlantic deep: | 1.8 x 10-7 ppm |
| Pacific surface: | 0.15 x 10-7 ppm |
| Pacific deep: | 1.65 x 10-7 ppm |
| Residence time: | 3000 years |
| Classification: | recycled |
| Oxidation state: | VI (mainly) and IV |
Source: Emsley, J. (1998) The Elements (3rd Edition)
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