BOILING POINT : 1,484°C
DENSITY : 1.55 g/cm 3
MOST COMMON IONS : Ca 2+
Calcium is the fifth most abundant element in Earth's crust, with calcium oxide, CaO (lime), being among the most common of all terrestrial compounds. Calcium is very important from a biological standpoint, being critical to bones, teeth, and shells of various animals, most often appearing in the form of insoluble calcium phosphate, Ca 3 (PO 4 ) 2 . Thus calcium is an important part of a healthy diet.
In elemental form, calcium is a relatively soft, silvery metal . Like other alkaline earths, it is too reactive to be found as a free element in nature. It was not until 1808 that Sir Humphry Davy isolated it by doing electrolysis on a mixture of lime (CaO) and mercuric oxide. Calcium's name comes from the Latin word calx , which means lime, a substance used since ancient Roman times in various ways, including as plasters for construction.
In addition to its biological role, calcium's presence is widespread in both nature and industry. As lime, it has many important commercial uses including in the treatment of drinking water and in the production and purification of iron and lead. Because of its usefulness, global consumption of lime exceeds 100 million tons annually. Other calcium compounds include calcium carbonate (CaCO 3 ), which is better known as limestone and is the principal component of stalactites and stalagmites in underground caves. Because it is a weak base, calcium carbonate is also used as an antacid. Calcium silicates (Ca 2 SiO 4 and Ca 3 SiO 5 ) are major ingredients in Portland cement, named because it resembles natural calcium minerals found on the Isle of portland in England. Calcium chloride (CaCl 2 ) is an excellent deicing and drying agent. In short, calcium is a very important and useful element.
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Krebs, Robert E. (1998). The History and Use of Our Earth's Chemical Elements: A Reference Guide. Westport, CT: Greenwood Press.
Swertka, Albert (2002). A Guide to the Elements. New York: Oxford University Press.