Boron is a chemical element . It has the chemical symbol B . It has the atomic number 5. It is a metalloid (it has properties of a metal and a non-metal ). Much boron is found in chemical compounds in its ore borax . Boron is never found free in nature.
Electrofluorochromic Properties of Aza Boron dipyrromethene
Quick Facts Pronunciation, Allotropes ...
Boron, 00 B boron (β-rhombohedral)
[1] Pronunciation (BOR -on ) Allotropes α-, β-rhombohedral, β-tetragonal (and more ) Appearance black-brown [ 10.806 , 10.821 ][2]
Group group 13 (boron group) Period period 2 Block p-block Electron configuration [ He ] 2s2 2p1 Electrons per shell 2, 3 Phase at STP solid Melting point 2349 K (2076 °C, 3769 °F) Boiling point 4200 K (3927 °C, 7101 °F) Density when liquid (at m.p. ) 2.08 g/cm3 Heat of fusion 50.2 kJ/mol Heat of vaporization 508 kJ/mol Molar heat capacity 11.087 J/(mol·K) Vapor pressure
P (Pa)
1
10
100
1 k
10 k
100 k
at T (K)
2348
2562
2822
3141
3545
4072
Oxidation states −5, −1, 0,[3] +1, +2, +3 [4] [5] (a mildly acidic oxide) Electronegativity Pauling scale: 2.04 Ionization energies 1st: 800.6 kJ/mol 2nd: 2427.1 kJ/mol 3rd: 3659.7 kJ/mol (more ) Atomic radius empirical: 90 pm Covalent radius 84±3 pm Van der Waals radius 192 pm Spectral lines of boronNatural occurrence primordial Crystal structure rhombohedral Speed of sound thin rod 16,200 m/s (at 20 °C) Thermal expansion β form: 5–7 µm/(m⋅K) (at 25 °C)[6] Thermal conductivity 27.4 W/(m⋅K) Electrical resistivity ~106 Ω⋅m (at 20 °C) Magnetic ordering diamagnetic [7] Molar magnetic susceptibility −6.7·10−6 cm3 /mol[8] Mohs hardness ~9.5 CAS Number 7440-42-8 Discovery Joseph Louis Gay-Lussac and Louis Jacques Thénard [9] (30 June 1808)First isolation Humphry Davy [10] (9 July 1808)
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Boron in a tube
Two types of boron are found (allotropes ). Amorphous boron is a brown powder and metallic (crystalline ) boron is black and hard and a weak conductor at room temperature . Boron is the 5th element in the periodic table and is part of the Earth's surface.
Pure boron is used as a dopant (a substance added to semiconductors to change how it behaves with electricity ) in the semiconductor industry . Chemical compounds of boron are important as to make strong materials not weigh very much, as nontoxic insecticides and preservatives , and for chemical synthesis .
Plants need boron in them to live. Very small amounts of boron are needed in animal 's bodies so that they are very healthy . How it keeps animals healthy is not known in detail.
Boron was discovered by Sir Humphry Davy , an English chemist, in 1808.
Boron melts at 2075 °C (3767 °F), and boils at 4000 °C (7232 °F).