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Calcium is a soft grey metallic element belonging to the group II of the periodic table. It is characterised by

1. Atomic number 20
2. Relative atomic mass 40.08
3. Relative density 1.55
4. Melting point 840^OC
5. Boiling point 1484^OC

Calcium compounds are common in the earth’s crust. In the earth’s crust it occurs as limestone and marble (CaCO₃), gypsum (CaSO₄.2H₂O) and fluorite (CaF₂).