Boron

Boron, chemical symbol B, is a rare element present in only 0.0003% of the earth's crust, mostly found in dry lake beds in the western United States in the form of borax (Na₂B₄O₅(OH)₅• 8H₂O), and kernite ((Na₂B₄O₅(OH)₅•2H₂O), which are hydrated sodium salts of tetraboric acid. Borax is mildly alkiline and is used as a cleansing agent. In addition, due its low melting temperature, boron is used in flux for soldering and welding. Some boron compounds are Lewis acids and many boron compounds form three-center two-electron bonds.

boric acids

Boric acid, H₃BO₃, is a mildly acid antiseptic formed from the reaction of borax with sulfuric acid. Boric acids include orthoboric acid (H₃BO₃), metaboric acid (HBO₂) and tetraboric (or pyroboric) acid (H₂B₄O₇).

boron halides

All four boron trihalides are planar, non-polar, covalent compounds. Boron trifluoride is a gas, boron triiodide is a solid and boron trichloride and tribromide are liquids. Boron trihalides are Lewis acids and react readily with water to produce boric acid and the corresponding hydrogen halide.

boron hydrides

Boron hydrides are excellent sources of the hydride ion H^- and thus are good reducing agents. Sodium borohydride, NaBH₄, is a reducing agent used in many inorganic and organic reactions. Lithium borohydride (LiB₄) and aluminum borohydride (Al(BH₄)₃ are also common borohydrides used in chemistry. The reduction of ketones to secondary alcohols is a typical use for these reagents. Boron hydrides can fall in one of two categories, those with formula B_nH_n+4 or the less stable formula B_nH_n+6

elemental boron

Elemental boron exists in a number of allotropes. $alfa$-rhombohedral boron is the simplest structure. All forms are polyhedral clusters of boron atoms, are semi-conductors and are very hard materials. All forms of elemental boron contain both three-center two-electron bonds as well as the typical two-center two-electron bonds found in most molecules.