|Name: calcium||Group number: 2|
|Symbol: Ca||Group name: Alkaline earth metal|
|Atomic number: 20||Period number: 4|
|Atomic weight: 40.078 (4) g||Block: s-block|
|CAS Registry ID: 7440-70-2||Voice: |
|Standard state: solid at 298 K||Colour: silvery white|
|Classification: Metallic||Availability: |
This sample is from The Elements Collection, an attractive and safely packaged collection of the 92 naturally occurring elements that is available for sale.
Calcium is a metallic element, fifth in abundance in the earth"s crust, of which it forms more than 3%. It is an essential constituent of leaves, bones, teeth, and shells.
The metal is a silvery colour and is rather hard. 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.
Calcium does not occur free in nature. Calcium is found mostly as limestone, gypsum and fluorite. Stalagmites and stalactites contain calcium carbonate.
IsolationHere is a brief summary of the isolation of calcium.
Calcium metal is readily available commercially and there is no need to make it in the laboratory. Commercially it can be made by the electrolysis of molten calcium chloride, CaCl2.
cathode: Ca2+(l) + 2e- Caanode: Cl-(l) 1/2Cl2 (g) + e-
The calcium chloride is made by the action of hydrochloric acid upon calcium carbonate. Calcium chloride is also a byproduct in the Solway process used to make sodium carbonate.
CaCO3 + 2HCl CaCl2 + H2O + CO2
Alternatively, and on small scale, calcium can be made through the reduction of CaO with aluminium or of CaCl2 with sodium metal
6CaO + 2Al 3Ca + Ca3Al2O6
CaCl2 + 2Na Ca + 2NaCl