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Oxidation & Electrons | Appearance & Characteristics Reactions | Compounds | Radius | Conductivity Abundance & Isotopes 
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General:
| Name: Boron | Symbol: B |
| Type: Metalloid | Atomic weight: 10.81 |
| Density @ 293 K: 2.34 g/cm3 | Atomic volume: 4.6 cm3/mol |
| Discovered: Boron was first isolated in 1808 by Sir Humphry Davy in London and by French chemists Joseph L. Gay-Lussac and L. J. Thénard. | |
States
| State (s, l, g): solid | |
| Melting point: 2348 K (2075 oC) | Boiling point: 4000 K (3727 oC) |
Energies
| Specific heat capacity: 1.02 J g-1 K-1 | Heat of atomization: 563 kJ mol-1 |
| Heat of fusion: 50.2 kJ mol-1 | Heat of vaporization (sublimation): 480 kJ mol-1 |
| 1st ionization energy: 800.6 kJ mol-1 | 2nd ionization energy: 2427.1 kJ mol-1 |
| 3rd ionization energy: 3659.7 kJ mol-1 | Electron affinity: 26.7 kJ mol-1 |
Oxidation & Electrons
| Shells: 2,3 | Electron configuration: [He] 2s2 2p1 |
| Minimum oxidation number: 0 | Maximum oxidation number: 0 |
| Min. common oxidation no.: 3 | Max. common oxidation no.: 3 |
| Electronegativity (Pauling Scale): 2.04 | Polarizability volume: 3 Å3 |
Appearance & Characteristics
| Structure: rhombohedral; B12 is icosahedral. | Color: black |
| Harmful effects: Elemental boron is not known to be toxic. | Hardness: 9.3 mohs |
| Characteristics: Metallic boron is extremely hard and has a high melting point. It exists in many polymorphs (different crystal lattice structures). Boron can transmit portions of infrared light. Boron is a poor conductor of electricity at room temperature but a good conductor at high temperature. | |
| Uses: Boron oxide (B2O3) is used in glassmaking and ceramics. Borax (Na2B4O7.10H2O) is used in making fiberglass, as a cleansing fluid and a water softener. Boric acid (H3BO3) is used as a mild antiseptic. Boron carbide (B4C) is used in tank armor and bullet proof vests. | |
Reactions
| Reaction with air: mild, w/ht ⇒ B2O3 | Reaction with 6 M HCl: none |
| Reaction with 15 M HNO3: none | Reaction with 6 M NaOH: none |
Compounds
| Oxide(s): B2O3 | Chloride(s): BCl3 and many BxCly |
| Hydride(s): B2H6 and many BxHy |
Radius
| Atomic radius: 85 pm | Ionic radius (1+ ion): pm |
| Ionic radius (2+ ion): pm | Ionic radius (3+ ion): 41 pm |
| Ionic radius (2- ion): pm | Ionic radius (1- ion): pm |
Conductivity
| Thermal conductivity: 27.4 W m-1 K-1 | Electrical conductivity: 5.0 x10-4 S cm-1 |
Abundance & Isotopes
| Abundance earth's crust: 8.7 ppm by weight, 17 ppm by moles | |
| Abundance solar system: 2 parts per billion by weight, 0.2 parts per billion by moles | |
| Cost, pure: 500 $/100g | |
| Cost, bulk: $/100g | |
| Source: Important sources of boron are Na2B4O6(OH)2.3H2O - known as rasorite or kernite; borax ore (known as tincal); and colemanite (CaB3O4(OH)4.H2O). Boron also occurs as orthoboric acid in certain volcanic spring waters. | |
| Isotopes: 11 whose half-lives are known, with mass numbers 7 to 17. Of these, two are stable: 10B and 11B. 10B is used in nuclear reactors as a neutron-capturing substance. | |
