A nonmetallic chemical element occuring only in combination, as with sodium and oxygen in borax, and produced in the form of either a brown amorphous powder or very hard, brilliant crystals. Its compounds are used in the preparation of boric acid, water softeners, soaps, enamels, borosilicate glasses, and pottery, in the manufacture of insulation fiberglass and sodium perborate bleach, and in the treatment of arthritis. The isotope boron-10 is used as a control for nuclear reactors, as a shield for radiation, and in instruments used for detecting neutrons. With titanium and tungsten, boron is used to make heat-resistant alloys for jets and rockets.

Boron was first isolated in 1808 by Sir Humphry Davy (who named it after borax, one of its compounds), Joseph-Louis Gay-Lussac, and Louis-Jacques Thénard in London, England, through the reaction of boric acid with potassium.

Symbol: B
Atomic number: 5
Atomic weight: 10.811
Density (at room temperature and pressure): 2.34 g/cm3
Melting point: 2,080°C
Boiling point: 4,000°C
Valence: +3
Ground state electron configuration: [He]2s22p1