Symbol:

B

Atomic Number:

5

Atomic Weight:

10.81

Density:

2.34 cryst. gm/cc

Melting Point:

2079 ^oC

Boiling Point:

2550 ^oC

Thermal Conductivity:

0.274 W/cm/K @ 298.2 K

Electrical Resistivity:

1.8 x 1012 microhm-cm @ 0 ^oC

Electronegativity:

2.0 Paulings

Specific Heat:

0.245 Cal/g/K @ 25 ^oC

Heat of Vaporization:

128 K-Cal/gm atom at 2550 ^oC

Heat of Fusion:

5.3 Cal/gm mole

Heat of Sublimation:

133 + 4 K-Cal/mole @ 0 K

Vapor Pressure:

4.6 x 10-4 to 8.5 x 10-3 mm @2200 K

Heat of Combustion with O₂:

150.49 K-Cal/mole @ 25 ^oC

149.79 K-Cal/mole @ 450 ^oC

Crystal Structure:

a-rhomohedral, b-rhombohedral and possible other forms

Energy Gap:

About 1.4 ev. @ 0 K

Hardness, Knoop:

100 gm load: 2500

Hardness, Mohs:

Approx. 9.3

Coefficient of expansion mean:

20-750 ^oC: 8.3 x 10-6 ^oC

Specific Magnetic Susceptibility:

-0.62 x 10-6 cgs @ 2000 ^oC (Diamagnetic)

Ductility:

Brittle

Bending Strength:

76,000 psi

Heat Content (Enthalpy):

290.4 Cal/mole @ 298.16 K

22,630 Cal/mole @ 3000 K

Entropy:

1.4 Cal/deg/mole @ 298.16 K; 16.5 @ 3000 K

Heat Capacity:

2.65 Cal/deg/mole @ 298.16 K; 7.1 @ 1200 K