# Boron

Boron, 5B| boron (β-rhombohedral) |
| Boron |
| Pronunciation | /ˈbɔːrɒn/ ​(BOR**-on*) |
| Appearance | black-broun |
| Standard atomic weight *A*r, std(B) | [7001108059999999999♠10.806, 7001108210000000000♠10.821] conventional: 7001108100000000000♠10.81 |
| Boron in the periodic cairt |
|

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|

|  |  |  |
| --- | --- | --- |
| Hydrogen |  | Helium |
| Lithium | Beryllium |  | Boron | Carbon | Nitrogen | Oxygen | Fluorine | Neon |
| Sodium | Magnesium |  | Aluminium | Silicon | Phosphorus | Sulfur | Chlorine | Argon |
| Potassium | Calcium |  | Scandium | Titanium | Vanadium | Chromium | Manganese | Airn | Cobalt | Nickel | Capper | Zinc | Gallium | Germanium | Arsenic | Selenium | Bromine | Krypton |
| Rubidium | Strontium |  |  | Yttrium | Zirconium | Niobium | Molybdenum | Technetium | Ruthenium | Rhodium | Palladium | Siller (element) | Cadmium | Indium | Tin | Antimony | Tellurium | Iodine | Xenon |
| Caesium | Barium | Lanthanum | Cerium | Praseodymium | Neodymium | Promethium | Samarium | Europium | Gadolinium | Terbium | Dysprosium | Holmium | Erbium | Thulium | Ytterbium | Lutetium | Hafnium | Tantalum | Tungsten | Rhenium | Osmium | Iridium | Platinum | Gowd | Mercur (element) | Thallium | Leid (element) | Bismuth | Polonium | Astatine | Radon |
| Francium | Radium | Actinium | Thorium | Protactinium | Uranium | Neptunium | Plutonium | Americium | Curium | Berkelium | Californium | Einsteinium | Fermium | Mendelevium | Nobelium | Lawrencium | Rutherfordium | Dubnium | Seaborgium | Bohrium | Hassium | Meitnerium | Darmstadtium | Roentgenium | Copernicium | Ununtrium | Flerovium | Ununpentium | Livermorium | Ununseptium | Ununoctium |

 | - ↑ **B** ↓ Al |
| beryllium ← **boron** → carbon |

 |

 |
| Atomic nummer (*Z*) | 5 |
| Group | group 13 (boron group) |
| Period | period 2  |
| Block | p-block  |
| Element category |   Metalloid |
| Electron confeeguration | [He] 2s2 2p1 |
| Electrons per shell | 2, 3 |
| Pheesical properties |
| Phase at STP | solit |
| Meltin pynt | 2349 K ​(2076 °C, ​3769 °F)  |
| Bylin pynt | 4200 K ​(3927 °C, ​7101 °F)  |
| Density when liquid (at m.p.) | 2.08 g/cm3  |
| Heat o fusion | 50.2 kJ/mol  |
| Heat o vapourisation | 480 kJ/mol  |
| Molar heat capacity | 11.087 J/(mol·K)  |
| **Vapour pressur**

| *P* (Pa) | 1 | 10 | 100 | 1 k | 10 k | 100 k |
| --- | --- | --- | --- | --- | --- | --- |
| at *T* (K) | 2348 | 2562 | 2822 | 3141 | 3545 | 4072 |

 |
| Atomic properties |
| Oxidation states | −5, −1, 0, +1, +2, **+3** (a mildly acidic oxide) |
| Electronegativity | Pauling scale: 2.04  |
| Ionisation energies | * (more)
 |
| Atomic radius | empirical: 90 pm  |
| Covalent radius | 84±3 pm  |
| Van der Waals radius | 192 pm  |
| Colour lines in a spectral range**Spectral lines o boron** |
| Ither properties |
| Naitural occurrence | primordial |
| Creestal structur |  ​rhombohedral |
| Speed o soond  thin rod | 16,200 m/s (at 20 °C)  |
| Thermal expansion | (β form) 5–7 µm/(m·K) (at 25 °C)  |
| Thermal conductivity | 27.4 W/(m·K)  |
| Electrical resistivity | ~106  Ω·m (at 20 °C)  |
| Magnetic orderin | diamagnetic  |
| Mohs haurdness | ~9.5  |
| CAS Nummer | 7440-42-8  |
| History |
| Diskivery | Joseph Louis Gay-Lussac an Louis Jacques Thénard (30 June 1808) |
| First isolation | Humphry Davy (9 Julie 1808) |
| Main isotopes o boron |
|

| Iso­tope | Abun­dance | Hauf-life (*t*1/2) | Decay mode | Pro­duct |
| --- | --- | --- | --- | --- |
| 10B | 19.9(7)% | stable |
| 11B | 80.1(7)% | stable |

 |
| 10B content may be as low as 19.1% and as high as 20.3% in natural samples. 11B is the remainder in such cases. |
|

**Boron** is a chemical element wi symbol **B** an atomic nummer 5. Acause boron is produced entirely bi cosmic ray spallation an nae bi stellar nucleosynthesis, it is a law-abundance element in baith the solar seestem an the Yird's crust. Boron is concentratit on Yird bi the watter-solubility o its mair common naiturally occurrin compoonds, the borate minerals. Thir are mined industrially as evaporites, sic as borax an kernite.