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| Atomic Number: | 20 | Atomic Symbol: | Ca | | Atomic Weight: | 40.08 | Electron Configuration: | 2-8-8-2 | | Shells: | 2,8,8,2 | Filling Orbital: | 4s2 | | Melting Point: | 839oC | Boiling Point: | 1484oC | | Uses: | bones & shells in life forms, cement and plaster of paris |
History(L. calx, lime) Though lime was prepared by the Romans in the
first century under the name calx, the metal was not dicovered until 1808. After
learning that Berzelius and Pontin prepared calcium amalgam by electrolyzing
lime in mercury, Davy was able to isolate the impure metal.
SourcesCalcium 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.
PropertiesThe 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.
UsesThe 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.
CompoundsIts 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 stalgmites and is responsible for
hardness in water. Other important compounds are the carbide, chloride,
cyanamide, hypochlorite, nitrate, and sulfide.
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