Carbonate ($C{O}_3^{2-}$)

The carbonate ion is $\mathrm{C}{\mathrm{O}}_3^{2-}$, with a planar carbon-oxygen framework and delocalized bonding. Its protonated relative is bicarbonate, $\mathrm{HC}{\mathrm{O}}_3^{-}$.

Carbonate salts, dissolved carbon dioxide, and these protonation states are linked by acid-base and solubility equilibria. Adding acid can release carbon dioxide, while changing pH can alter which carbonate-containing solids are stable.