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Bor (B)
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Bor 5Pb10.811
1808 von L.J. Lussac und L.J. Thenard in Paris, Frankreich und von Sir Humphry Davy in London, UK, entdeckt.
[Arabic, buraq]
French: bore
English: Boron
Italian: boro
Spanish: boro
Beschreibung: Nichtmetall, tritt in mehreren Modifikationen auf. Amorphes Bor ist ein dunkles Pulver, das nicht mit Sauerstoff, Wasser, Säuren und Basen reagiert. Es bildet mit den meisten Metallen Metallboride. Verwendet in Borosilicatgläsern und Detergentien.
Further Materials properties
| Crystal structure: |
(cell dimensions/pm), space group, |
|---|---|
| X-ray diffractions mass absorption coefficients: | CuKa 2.39 (µ/r) / cm2g-1 MoKa 0.392 (µ/r) / cm2g-1 |
| Neutron scattering length: | 0.535 b/10-12 cm |
| Thermal neutron capture cross-section: | 767 sa / barns |
| Density: | 2340 (β-rhomb.) kg/m-3 [293 K] |
| Melting point: | 2299.85 °C / 2573 °K |
| Boiling point: | 3657.85 °C / 3931 °K |
| Molar volume: | 4.62 cm3 |
| Thermal conductivity: | 27.0 [300 K] Wm-1K-1 |
| Coefficient of linear thermal expansion: | 5 x 10-6 K-1 |
| Electrical resistivity: | 18 000 [273 K] Ωm |
| Mass magnetic susceptibility: | -7.8 x 10-9 (s) kg-1m3 |
| Radi: | B3+ 23; atomic 83; covalent 88; van der Waals 208 |
| Electronegativity: | 2.04 (Pauling); 2.01 (Allred); 4.29 eV (absolute) |
| Effective nuclear charge: | 2.60 (Slater); 2.42 (Clementi); 2.27(Froese-Fischer) |
| Number of Isotopes (incl. nuclear isomers): | 6 |
| Isotope mass range: | 8 -> 13 |
Biological data
| Biological role: | Essential to plants; toxic in excess |
|---|---|
| Toxicity | |
| Toxic intake: | 5 g (boric acid) |
| Lethal intake: | 10 - 20 g (boric acid). LD50 (boric acid, oral, rat) = 2.66g kg-1 |
| Hazards: | Boric acid and borates are a human poison in excess, althrough once used in medicines. |
| Level in humans | |
| Blood: | 0.13 mg dm-3 |
| Bone: | 1.1 - 3.3 ppm |
| Liver: | 0.4 - 3.3 ppm |
| Muscle: | 0.33 - 1 ppm |
| Daily dietary intake: | 1 - 3 mg |
| Total mass of element in average [70 kg] person: |
18 mg |
Geological data
| Minerals: | ||||
|---|---|---|---|---|
| Mineral | Formula | Density | Hardness | Crystal apperance |
| Borax | Na2B4O5(OH)4.8H2O | 1.715 | 2 - 2.5 | mon., vit. /res./ earthy colourless |
| Colemanite | CaB2O4(OH)3.H2O | 2.423 | 4.5 | mon., vit./adam. colourless |
| Datolite | CaBSiO4(OH) | 3.0 | 5 - 5.5 | mon., vit. white |
| Kernite | Na2B4O6.(OH)2.3H2O | 1.908 | 2.5 | mon. vit. colourless |
| Ulexite | NaCaB5O6(OH)6.5H2O | 1.955 | 2.5 | tric., silky/ vit. colourless |
| Chief ores: | kernite, borax, ulexite, colemanite |
|---|---|
| World production: | 1 x 106 (B2O3) tonnes/year |
| Main mining areas: | ulexite in USA, Tibet, Chile; colemanite in USA, Turkey |
| Reserves: | 270 x 106 tonnes as B2O3 |
| Specimen: | available as crystals, pieces or powder. Safe. Safe. |
| Abundances | |
|---|---|
| Sun: | 2.63 x 105 (relative to H = 1 x 1012) |
| Earth's crust: | 950 ppm |
| Seawater | 4.41 ppm |
| Residence time: | 1 x 107 years |
| Classification: | accumulating |
| Oxidation state: | III |
Source: Emsley, J. (1998) The Elements (3rd Edition)
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