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berylliumboroncarbon


B

Al
Appearance
black-brown
General properties
Name, symbol, number boron, B, 5
Group, period, block 132, p
Standard atomic weight {{{atomic mass}}} g/mol
Electron configuration [He] 2s2 2p1
Electrons per shell 2, 3 (Image)
Physical properties
Phase solid
Liquid density at m.p. 2.08 g/cm3
Melting point 2349 K, 2076 °C, 3769 °F
Boiling point 4200 K, 3927 °C, 7101 °F
Heat of fusion 50.2 kJ/mol
Heat of vaporization 508 kJ/mol
Specific heat capacity (25 °C) 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
Atomic properties
Oxidation states 3, 2, 1, −1, −5
((a mildly acidic oxide))
Electronegativity 2.04 (Pauling scale)
Ionization energies
1st: {{{1st ionization energy}}} kJ/mol
2nd: {{{2nd ionization energy}}} kJ/mol
3rd: {{{3rd ionization energy}}} kJ/mol
Atomic radius 90 pm
Covalent radius 84±3 pm
Van der Waals radius 192 pm
Miscellanea
Crystal structure rhombohedral
Magnetic ordering diamagnetic
Electrical resistivity (20 °C) ~106Ω·m
Thermal conductivity (300 K) 27.4 W/(m·K)
Thermal expansion (25 °C) β form: 5–7 µm/(m·K)
Speed of sound (thin rod) (20 °C) 16,200 m/s
Mohs hardness ~9.5
CAS registry number 7440-42-8
Most stable isotopes
Main article: Isotopes of boron
iso NA half-life DM DE (MeV) DP
10B 20% stable
11B 80% 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.
B,5
Boron in a tube

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.

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 it is part of the earths 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 a lot of 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).

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