Name: calcium
Symbol: Ca
Atomic number: 20
Atomic weight: 40.078 (4) g
Group in periodic table: 2
Group name: Alkaline earth metal
Period in periodic table: 4
Block in periodic table: s-block
CAS registry ID: 7440-70-2
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.