The periodic table/Boron

Discovery
Boron was discovered by J.L. Gay-Lussac and L.J. Thenard in Paris, France, and independently by Sir Humphry Davy in London, UK in 1808. The name is derived from the Arabic 'buraq', which was the name for borax.

Quick Facts
Name: Boron

Symbol: B

Mass: 10.811

Atomic Number: 5

Electron Configuration: [He] 2s2 2p1

Classification: metalloid

CAS Number: 7440-42-8

Appearance: dark amorphous powder

Discovery in: 1808

Key Isotopes: 11B

Allotropes: α-rhombohedral B, β-rhombohedral B, γ-B, tetragonal boron

Density: 2.34 g/L

Crystal Structure: rhombohedral

Melting Point: 2077 °C

Boiling Point: 4000 °C

Uses
Amorphous boron is used in pyrotechnic flares to provide a distinctive green colour, and in rockets as an igniter. The most important compounds of boron are boric (or boracic) acid, widely used as a mild antiseptic, and borax which serves as a cleansing flux in welding and as a water softener in washing powders. Boron compounds are also extensively used in the manufacture of borosilicate glasses. Pyrex glass is tough and heat resistant because of the boric acid used to make it. The isotope boron-10 is used as a control for nuclear reactors, as a shield for nuclear radiation, and in instruments used for detecting neutrons.

Elemental boron is not considered a poison, but assimilation of its compounds has a cumulative toxic effect. Boron is an essential mineral for plants but not animals - in fact it can be toxic in excess. We take in about 2 milligrams each day from our food (about 60 grams in a lifetime). Some boron compounds show promise in treating arthritis.

Atomic Data
Atomic radius: 1.920 Å

Covalent radius: 0.84 Å

Electronegativity: 2.040

Electron affinity: 26.98 kJ mol-1

Ionisation energies

First: 800.638 kJ mol-1

Second: 2427.067 kJ mol-1

Third: 3659.748 kJ mol-1

Fourth: 25025.884 kJ mol-1

Fifth: 32826.774 kJ mol-1

Supply Risk
Scarcity factor: 4.5 (low risk)

Crustal abundance: 11 ppm

Reserve base distribution: n/a

Production concentration: 33.6%

Top 3 countries for mining:
 * 1) Turkey
 * 2) Russia
 * 3) Canada

Top 3 countries for production:
 * 1) Turkey
 * 2) USA
 * 3) Chile

Oxidation States and Isotopes
Common oxidation states: 3

Isotopes

Pressure and Temperature Data
Molar heat capacity: 11.087 J mol-1 K-1