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Boron (B)
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Boron 5Pb10.811
Boron was discovered in 1808 by L.J. Lussac and L.J. Thenard in Paris, France and Sir Humphry Davy in London, England.
[Arabic, buraq]
French: bore
German: Bor
Italian: boro
Spanish: boro
Description: Boron is a non-metal element with several forms - the most common is amorphous boron, which is a dark powder, unreactive to oxygen, water, acids and alkalis. It reacts with metals to form borides. Boron compounds are used in borosilicate glass, detergents and fire-retardants.
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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