Calcium, Ca, is an alkaline earth metallic element, found in
Group IIa of
the periodic table.
Atomic Number : 20
Relative Atomic Mass : 40.08
Discovery
Calcium has been known from the earliest times and lime-burning
was carried out by the Romans.
Calcium was first isolated as a metal by
Sir Humphery Davy in 1808AD.
Occurrence
Calcium is widely found as its carbonate being a constituent of rocks.
Chalk, limestone and marble are different crystalline forms of calcium
carbonate which occur in mountain ranges. The mixed carbonate, Dolomite,
also occurs in mountain rocks.
Other important minerals include
Gypsum, MgSO4.2H2O,
Fluorospar, CaF2,
Apatite, 3Ca3(PO4)2CaF2,
Diopside, CaMg(SiO3)2, and
Lime Felspar, CaAl3Si2O8.
Calcium also occurs as soluble salts in natural waters
and is responsible for its hardness.
Extraction
Preparation
Manufacture
Calcium is prepared by the Electrolysis
of fused anhydrous calcium chloride and calcium fluoride at 700 degC.
Properties
Calcium is a silver-white lustrous metal, which tarnishes
slowly in air.
Calcium is as approximately as hard as tin.
Reactions
Calcium is highly reactive chemically, and oxidised slowly in air.
Calcium burns rapidly when heated in air to form calcium oxide.
2 Ca + O2 ==> 2 CaO
Calcium reacts with water to form calcium hydroxide and hydrogen.