In chemistry, a carbonate is a salt of carbonic acid (H2CO3),characterized by the presence of the carbonate ion, a polyatomic ionwith the formula of CO2−
The name may also mean an ester of carbonic acid, an organic compound containing the carbonate groupC(=O)(O–)2.

The term is also used as a verb, to describe carbonation: the process of raising the concentrations of carbonate and bicarbonate ions in water to produce carbonated water and other carbonated beverages – either by the addition of carbon dioxide gas under pressure, or by dissolving carbonate or bicarbonate salts into the water.
Cerium Carbonate   Lanthanum Carbonate