The chemical element calcium is a malleable, light, silver while metal, an Alkaline Earth Metal of Group IIA in the periodic table. Its symbol is Ca, its atomic number is 20, and its atomic weight is 40.08. Calcium was first prepared by Sir Humphrey Davy in 1808. following the method of J.J. Berzellus and M.M. Pontin. Davy electrolyzed a mixture of lime, CaO, and mercury to produce an amalgam (a mercury, he obtained a calcite, a form of calcium carbonate (CaCO 3 ). Occurrence In cosmic abundance calcium is 13 th among the elements; on Earth it ranks 5 th and forms 3.2 % of the Earth’s crust, being less prevalent than aluminum (7.3%) or Iron (4.1%). It is not found free in nature but is common as the carbonate rock limestone, CaCO 3. It is also well distributed as the minerals calcium phosphate, silicate, fluoride, and sulfate. As calcium-magnesium carbonate it is one of the principal components of dolomite minerals and is found in pearls, coral, natural chalk, calcite, onyx