Beryllium is the chemical element with the symbol "Be" and atomic number 4. It is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl (aquamarine, emerald) and chrysoberyl. As a free element it is a steel-gray, strong, lightweight and brittle alkaline earth metal. The commercial use of beryllium metal presents technical challenges due to the toxicity (especially by inhalation) of beryllium-containing dusts. Beryllium is corrosive to tissue, and can cause a chronic life-threatening allergic disease called berylliosis in some people. As it is not synthesized in stars, beryllium is a relatively rare element in both the Earth and the universe. The element is not known to be necessary or useful for either plant or animal life. Beryllium has exceptional flexural rigidity (Young's modulus 287 GPa) and a reasonably high melting point. The modulus of elasticity of beryllium is approximately 50% greater than that of steel. 9 4Be + 4 2He --> 12 6C + n , where 4 2He is an alpha particle and 12 6C is a carbon-12 nucleus Beryllium contains only one stable isotope, 9Be, and therefore is a monoisotopic element. Cosmogenic 10Be is produced in the atmosphere of the Earth by the cosmic ray spallation of oxygen and nitrogen. Beryllium is scarce in the universe. With a concentration of 1 part per billion (ppb) by weight, it is much less abundant than all elements preceding niobium, with the exception of boron, which has a similar abundance. Early analyses of emeralds and beryls always yielded similar elements, leading to the fallacious conclusion that both substances are aluminium silicates. René Just Haüy discovered that both crystals show strong similarities, and he asked the chemist Louis-Nicolas Vauquelin for a chemical analysis. Vauquelin was able to separate the aluminium from the beryllium by dissolving the aluminium hydroxide in an additional alkali. The direct electrolysis of a molten mixture of beryllium fluoride and sodium fluoride by Paul Lebeau in 1898 resulted in the first pure samples of beryllium.It took until World War I (1914–18) before significant amounts of beryllium were produced, but large-scale production was not started until early 1930s. It saw a rapid increase during World War II, due to the rising demand for hard beryllium-copper alloys and phosphors for fluorescent lights. References ^ "Beryllium: Beryllium(I) Hydride compound data". bernath.uwaterloo.ca. Retrieved 2007-12-10. ^ Lide, D. R., ed (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. p. 14-39. ISBN 0-8493-0486-5. ^Behrens, V. (2003). "11 Beryllium". In Beiss, PLandolt-Börnstein – Group VIII Advanced Materials and Technologies: Powder Metallurgy Data. Refractory, Hard and Intermetallic Materials. 2A1. Berlin: Springer. pp. 1–11. doi:10.1007/10689123_36. ISBN 978-3-540-42942-5. ^Hausner, Henry H. "Nuclear Properties". Beryllium its Metallurgy and Properties. University of California Press. p. 239. ^ "Beryllium: Isotopes and Hydrology". University of Arizona, Tucson. Retrieved 10 April 2011. ^ Whitehead, N; Endo, S; Tanaka, K; Takatsuji, T; Hoshi, M; Fukutani, S; Ditchburn, Rg; Zondervan, A (Feb 2008). "A preliminary study on the use of (10)Be in forensic radioecology of nuclear explosion sites". Journal of environmental radioactivity 99 (2): 260–70. doi:10.1016/j.jenvrad.2007.07.016. PMID 17904707. ^ Boyd, R. N.; Kajino, T. (1989). "Can Be-9 provide a test of cosmological theories?". The Astrophysical Journal 336: L55. Bibcode 1989ApJ...336L..55B. doi:10.1086/185360. ^ Arnett, David (1996). Supernovae and nucleosynthesis. Princeton University Press. p. 223. ISBN 0691011478. ^ Johnson, Bill (1993). "How to Change Nuclear Decay Rates". University of California, Riverside. Retrieved 2008-03-30. ^ Hammond, C. R. "Elements" in Lide, D. R., ed (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5. ^ Hansen, P. G.; Jensen, A. S.; Jonson, B. (1995). "Nuclear Halos". Annual Review of Nuclear and Particle Science 45: 591. Bibcode 1995ARNPS..45..591H. doi:10.1146/annurev.ns.45.120195.003111. ^ Ekspong, G. et al. (1992). Physics: 1981–1990. World Scientific. p. 172. ISBN 9789810207298.