Background

Boron is a black solid at room temperature that exhibits semi-metallic properties like silicon.
Discovery

Boron was discovered by Sir Humphrey Davy in 1808 when he reacted boric acid (HBO3) with potassium. Joseph-Louis Gay-Lussac and LJ Thernard also discovered Boron simultaneously in Paris.
Occurrence

Boron is not found in its elemental form in nature. It’s most important source is the mineral rasorite found in the Mojave Desert in California and extensive borax deposits in Turkey, as well as tourmaline and kernite.

It is also found in the minerals borax and colemanite and in certain volcanic spring waters.
Production

Several methods are employed to produce boron including:

· Vapour phase reduction of boron trichloride (BCl3)

· Reacting boron trichloride or boron tribromide with hydrogen on electrically heated filaments. This produces an impure amorphous boron which can be further refined by reacting with magnesium.

· Commercially produced by magnesium reduction of B2O3

Key Properties

Boron:

· Behaves like a semiconductor and has properties similar to silicon

· Is chemically inert resisting attack by acids such as HF and HCl

· Fine powder is attacked slowly by HNO3

· Is a poor electrical conductor at room temperature, but a good conductor at high temperatures

· Has an energy band gap of 1.50-1.65eV which is higher than for silicon or germanium



Property





Value

Symbol





B

CAS Number





7440-42-8

Atomic Number





5

Atomic Weight





10.81

Melting Point





2076°C

Boiling Point





3927°C

Density





2.46g/cm3

Applications

Boron is used for:

· Pyrotechnics where is produces a green colour

· An igniter in rockets

· In boric acid which is used as an antiseptic

· In borax which is used as a welding flux and washing powders