The carbonate ion is a polyatomic anion with the empirical formula CO32- and a molecular mass of 60.01 daltons; it consists of one central carbon atom surrounded by three identical oxygen atoms in a trigonal planar arrangement. The carbonate ion carries a negative two formal charge and is the conjugate base of the hydrogen carbonate ion, HCO3-, which is the conjugate base of H2CO3, carbonic acid.
"Copper in moist air slowly acquires a dull green coating. The green material is a 1:1 mole mixture of Cu(OH)
2 and CuCO
3:[1]"
2Cu(s) + H
2O(g) + CO
2 
Cu(OH)
2 + CuCO
3(s)
Copper carbonate decomposes at high temperatures, giving off carbon dioxide and leaving copper(II) oxide.
CuCO
3g(s)

CuO(s) + CO
2(g)
Following the filtration of the solution, the filtrate is dried under vacuum to produce magnesium carbonate as a hydrated salt:
Mg2+ + 2HCO3- ? MgCO3 + CO2 + H2O
When dissolved with acid, magnesium carbonate decomposes with release of carbon dioxide:
MgCO3 + 2HCl ? MgCl2 + CO2 + H2O
MgCO3+ H2SO4 ? MgSO4 + CO2 + H2O