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Atomic Number: 20
Atomic Symbol: Ca
Atomic Weight: 40.08
Electron Configuration: [Ar]4s2
History
(L. calx, lime) Though lime was prepared by the Romans in the first
century under the name calx, the metal was not discovered until 1808. After
learning that Berzelius and Pontin prepared calcium amalgam by electrolyzing
lime in mercury, Davy was able to isolate the impure metal.
Sources
Calcium is a metallic element, fifth in abundance in the earth's
crust, of which if forms more than 3%. It is an essential constituent of leaves,
bones, teeth, and shells. Never found in nature uncombined, it occurs abundantly
as limestone, gypsum, and fluorite. Apatite is the fluorophosphate or
chlorophosphate of calcium.
Properties
The metal has a silvery color, is rather hard, and is prepared by
electrolysis of the fused chloride to which calcium fluoride is added to lower
the melting point.
Chemically it is one of the alkaline earth elements; it readily
forms a white coating of nitride in air, reacts with water, burns with a
yellow-red flame, forming largely the nitride.
Uses
The metal is used as a reducing agent in preparing other metals such
as thorium, uranium, zirconium, etc., and is used as a deoxidizer, desulfurizer,
or decarburizer for various ferrous and nonferrous alloys. It is also used as an
alloying agent for aluminum, beryllium, copper, lead, and magnesium alloys, and
serves as a "getter" for residual gases in vacuum tubes, etc.
Compounds
Its natural and prepared compounds are widely used. Quicklime (CaO),
which is made by heating limestone that is changed into slaked lime by carefully
adding water, is the great base of chemical refinery with countless uses.
Mixed with sand it hardens as mortar and plaster by taking up
carbon dioxide from the air. Calcium from limestone is an important element in
Portland cement.
The solubility of the carbonate in water containing carbon
dioxide causes the formation of caves with stalactites and stalagmites and is
responsible for hardness in water. Other important compounds are the carbide,
chloride, cyanamide, hypochlorite, nitrate, and sulfide.
Sources: CRC Handbook of Chemistry and
Physics and the American Chemical Society.
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