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Reference


Boron
Chemical Properties & Compounds



Symbol Atomic Number Atomic Weight Melting Point Boiling Point Phase Density Classification
B 5 10.811 2076 °C 3927 °C Solid 2.34 g/cm3 Semi-Metal Toxic Element


5 beryllium ← boron → carbon
-
↑
B
↓
Al
General
Name, symbol, number boron, B, 5
Chemical series metalloids
Group, period, block 13, 2, p
Appearance black/brown
Standard atomic weight 10.811(7) g·mol−1
Electron configuration 1s2 2s2 2p1
Electrons per shell 2, 3
Physical properties
Phase solid
Density (near r.t.) 2.34 g·cm−3
Liquid density at m.p. 2.08 g·cm−3
Melting point 2349 K
(2076 °C, 3769 °F)
Boiling point 4200 K
(3927 °C, 7101 °F)
Heat of fusion 50.2 kJ·mol−1
Heat of vaporization 480 kJ·mol−1
Heat capacity (25 °C) 11.087 J·mol−1·K−1
Vapor pressure
P/Pa 1 10 100 1 k 10 k 100 k
at T/K 2348 2562 2822 3141 3545 4072
Atomic properties
Crystal structure rhombohedral
Oxidation states 3
(mildly acidic oxide)
Electronegativity 2.04 (Pauling scale)
Ionization energies
(more)		 1st: 800.6 kJ·mol−1
2nd: 2427.1 kJ·mol−1
3rd: 3659.7 kJ·mol−1
Atomic radius 85 pm
Atomic radius (calc.) 87 pm
Covalent radius 82 pm
Miscellaneous
Magnetic ordering nonmagnetic
Electrical resistivity (20 °C) 1.5×104Ω·m
Thermal conductivity (300 K) 27.4 W·m−1·K−1
Thermal expansion (25 °C) 5–7 µm·m−1·K−1
Speed of sound (thin rod) (20 °C) 16200 m/s
Bulk modulus (β form) 185 GPa
Mohs hardness 9.3
Vickers hardness 49000 MPa
CAS registry number 7440-42-8
Selected isotopes
Main article: Isotopes of boron
iso NA half-life DM DE (MeV) DP
10B 18.8%* B is stable with 5 neutrons
11B 81.2%* B is stable with 6 neutrons
*Boron-10 content may be as low as 19.1% and as
high as 20.3% in natural samples. Boron-11 is
the remainder in such cases.
References
Boron Compounds
Boron nitride

Source: Wikipedia article Boron


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Last updated: October 2007

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