The periodic table/Boron
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Subject classification: this is a chemistry resource. |
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Completion status: this resource is considered to be ready for use. |
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Type classification: this is an article resource. |
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Educational level: this is a research resource. |
Discovery
editBoron was discovered by J.L. Gay-Lussac and L.J. Thenard in Paris, France, and independently by Sir Humphry Davy in London, UK in 1808. The name is derived from the Arabic 'buraq', which was the name for borax.
Quick Facts
editName: Boron Symbol: B Mass: 10.811 Atomic Number: 5 Electron Configuration: [He] 2s2 2p1 |
Classification: metalloid CAS Number: 7440-42-8 Appearance: dark amorphous powder Discovery in: 1808 Key Isotopes: 11B Allotropes: α-rhombohedral B, β-rhombohedral B, γ-B, tetragonal boron |
Uses
editAmorphous boron is used in pyrotechnic flares to provide a distinctive green colour, and in rockets as an igniter. The most important compounds of boron are boric (or boracic) acid, widely used as a mild antiseptic, and borax which serves as a cleansing flux in welding and as a water softener in washing powders. Boron compounds are also extensively used in the manufacture of borosilicate glasses. Pyrex glass is tough and heat resistant because of the boric acid used to make it. The isotope boron-10 is used as a control for nuclear reactors, as a shield for nuclear radiation, and in instruments used for detecting neutrons.
Elemental boron is not considered a poison, but assimilation of its compounds has a cumulative toxic effect. Boron is an essential mineral for plants but not animals - in fact it can be toxic in excess. We take in about 2 milligrams each day from our food (about 60 grams in a lifetime). Some boron compounds show promise in treating arthritis.
Atomic Data
editAtomic radius: 1.920 Å Covalent radius: 0.84 Å Electronegativity: 2.040 Electron affinity: 26.98 kJ mol-1 |
Ionisation energies First: 800.638 kJ mol-1 Second: 2427.067 kJ mol-1 Third: 3659.748 kJ mol-1 Fourth: 25025.884 kJ mol-1 Fifth: 32826.774 kJ mol-1 |
Supply Risk
editScarcity factor: 4.5 (low risk)
Crustal abundance: 11 ppm Reserve base distribution: n/a Production concentration: 33.6% |
Top 3 countries for mining:
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Top 3 countries for production:
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Oxidation States and Isotopes
editCommon oxidation states: 3
Isotopes
| Isotope | Atomic mass | Abundance (%) | Half life | Mode of decay |
|---|---|---|---|---|
| 10B | 10.013 | 19.9 | ||
| 11B | 11.009 | 80.1 |
Pressure and Temperature Data
editMolar heat capacity: 11.087 J mol-1 K-1