Boron

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,^[11] 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.

Boron, ₅B

boron (β-rhombohedral)[1]
Boron
Pronunciation	/ˈbɔːrɒn/ ​(BOR-on)
Appearance	black-broun
Standard atomic weight Ar, 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,[2] +1, +2, +3[3][4] (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[5] µm/(m·K) (at 25 °C)
Thermal conductivity	27.4 W/(m·K)
Electrical resistivity	~106  Ω·m (at 20 °C)
Magnetic orderin	diamagnetic[6]
Mohs haurdness	~9.5
CAS Nummer	7440-42-8
History
Diskivery	Joseph Louis Gay-Lussac an Louis Jacques Thénard[7] (30 June 1808)
First isolation	Humphry Davy[8] (9 Julie 1808)
Main isotopes o boron
Iso­tope Abun­dance Hauf-life (t1/2) Decay mode Pro­duct 10B 19.9(7)% stable[9] 11B 80.1(7)% stable[9]
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.[10]
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