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Calcium

Ca

Atomic Number: 20
Atomic Weight: 40.078
Element Type: Alkali Earth Metal
Crystal Structure: Cubic Face Centered
Melting Point: 842.0°C = 1547.6°F = 1115.15 K
Boiling Point: 1484.0°C = 2703.2°F = 1757.15 K
Critical Temp: °C = °F = K
Atomic Radius: 2.23 Å (Å = Angstrom = 10-10 m)
Covalent Radius: 1.74 Å
Electronegativity: 1.0

Discovery

(L. calx, lime) Though lime was prepared by the Romans in the first century under thename calx, the metal was not discovered until 1808. After learning that Berzelius andPontin prepared calcium amalgam by electrolyzing lime in mercury, Davy was able to isolatethe impure metal.

Sources

The Romans prepared lime (called calx) in the first century, but the metal was not discovered until 1808. Berzelius and Pontin prepared calcium amalgam by electrolyzing lime in mercury. Davy isolated the impure metal. The metal may be prepared by electrolysis of CaCl2 at a temperature slightly above its melting point. Calcium is the fifth most abundant element in the earth's crust, making up 3.22% of the earth, air, and oceans. Natural forms of calcium include limestone (CaCO3), gypsum (CaSO4·2H2O), and fluorite (CaF2). Apatite is the fluorophosphate or chlorophosphate of calcium.

Uses

Calcium is essential for human nutrition. Animals skeletons get their rigidity primarily from calcium phosphate. The eggs of birds and shells of mollusks are comprised of calcium carbonate. Calcium is also necessary for plant growth. Calcium is used as a reducing agent when preparing metals from their halogen and oxygen compounds; as a reagent in purification of inert gases; to fix atmospheric nitrogen; as a scavenger and decarbonizer in metallurgy; and for making alloys. Calcium compounds are used in making lime, bricks, cement, glass, paint, paper, sugar, glazes, as well as for many other uses.


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