* Calcium is a member of the alkaline earth metals family:
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CALCIUM / Ca / 20
A silvery, relatively soft metal that corrodes easily. Six isotopes
are found in nature:
Ca<40/20> / 97%
Ca<44/20> / 2%
Ca<42/20> / 0.65%
Ca<48/20> / 0.2%
Ca<43/20> / 0.14%
Ca<46/20> / 0.004%
All are stable, except possibly Ca<48/20>, which may have a half-life
of about 6E18 years.
atomic weight: 40.078
abundance: 5th
density: 1.55 gm/cc
melting point: 839 C
boiling point: 1,484 C
valence: 2
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Calcium is very common and an extremely important biological element, since it makes up much of our bones; humans need to obtain a regular dose of calcium, though too much may contribute to kidney or bladder stones. Calcium is a very important building material, with gypsum -- CaSO4 * 2(H2O) -- commonly used in the manufacture of drywall, and marble is a form of calcium carbonate (CaCO3). Gypsum and calcium carbonate are important components of building cement and concrete. Lime (calcium oxide or CaO) is used in chemical synthesis. Production of lime is over a hundred million tonnes a year; production of calcium metal, which is used in some chemical synthesis processes and alloys, is only a few thousand tonnes a year.
