Boron

Boron compounds such as borax (sodium tetraborate, Na₂B₄O₇^.10H₂O) have been known and used by ancient cultures for thousands of years. Borax's name comes from the Arabic buraq, meaning "white." 

Boron was first partially isolated in 1808 by French chemists Joseph L. Gay-Lussac and L. J. Thénard and independently by Sir Humphry Davy in London. Gay-Lussac & Thénard reacted boric acid with magnesium or sodium to yield boron, a gray solid. (1) They believed it shared characteristics with sulfur and phosphorus and named it bore. (2)

Davy first tried to produce boron by electrolysis of boric acid, but was not satisfied with the results. He enjoyed greater success reacting boric acid with potassium in a hydrogen atmosphere. The result was a powdery substance. Davy commented the substance was, "of the darkest shades of olive. It is opake, very friable, and its powder does not scratch glass." After carrying out a number of chemical reactions to verify the uniqueness of the substance, Davy wrote, "there is strong reason to consider the boracic basis as metallic in nature, and I venture to propose for it the name of boracium." (2)

Neither party had, in fact, produced pure boron. Their samples were only about 60% pure. In 1909 William Weintraub was able to produce 99% pure boron, by reducing boron halides with hydrogen.

Almost a century later, in 2004, Jiuhua Chen and Vladimir L. Solozhenko produced a new form of boron, but were uncertain of its structure. In 2009, a team led by Artem Oganov was able to demonstrate the new form of boron contains two structures, B₁₂ icosohedra and B₂ pairs. ⁽³⁾ Gamma-boron, as it has been called, is almost as hard as diamond and more heat-resistant than diamond. Talking about boron's part metal, part non-metal properties, Oganov said, "Boron is a truly schizophrenic element. It's an element of complete frustration. It doesn't know what it wants to do. The outcome is something horribly complicated." ⁽⁴⁾

Elemental boron is not known to be toxic.

Boron is a metalloid, intermediate between metals and non-metals. It exists in many polymorphs (different crystal lattice structures), some more metallic than others. Metallic boron is extremely hard and has a very high melting point.

Boron does not generally make ionic bonds, it forms stable covalent bonds.

Boron can transmit portions of infrared light.

Boron is a poor room temperature conductor of electricity but its conductivity improves markedly at higher temperatures.

Boron is used to dope silicon and germanium semiconductors, modifying their electrical properties.

Boron oxide (B₂O₃) is used in glassmaking and ceramics.

Borax (Na₂B₄O₇.10H₂O) is used in making fiberglass, as a cleansing fluid, a water softener, insecticide, herbicide and disinfectant.

Boric acid (H₃BO₃) is used as a mild antiseptic and as a flame retardant.

Boron Nitride's hardness is second only to diamond, but it has better thermal and chemical stability, hence boron nitride ceramics are used in high-temperature equipment.

Boron nitride nanotubes can have a similar structure to carbon nanotubes. BN nanotubes are more thermally and chemically stable than carbon nanotubes and, unlike carbon nanotubes, boron nitride nanotubes are electrical insulators.

Boron carbide (B₄C) is used in tank armor and bullet proof vests.

Boron compunds are usually is found in sediments and sedimentary rock formations. The chief sources of boron are Na₂B₄O₆(OH)₂.3H₂O - known as rasorite or kernite; borax ore (known as tincal); and with calcium in colemanite (CaB₃O₄(OH)₄.H₂O). Boron also occurs as orthoboric acid in some volcanic spring wa

11 whose half-lives are known, with mass numbers 7 to 17. Of these, two are stable: ¹⁰B and ¹¹B. ¹⁰B is used in nuclear reactors as a neutron-capturing substance.

References
1. Alaa S. Abd-El-Aziz, Macromolecules Containing Metal and Metal-Like Elements Volume 8 Boron-Containing Polymers., (2007) p2. Wiley-Interscience
2. Walter Channing, John Ware, New-England Journal of Medicine and Surgery, and Collateral Branches of Science., (1812) p220. T. B. Wait and Co. (pdf download 19.8 MB)
3. Artem R. Oganov et al, Ionic high-pressure form of elemental boron., Nature 457, 863-867 (12 February 2009)
4. Kenneth Chang, Theory and Experiment Meet, and a New Form of Boron Is Found., (February 2, 2009) New York Times Online