C 1s - Carbonates

The C 1s binding energy average for carbonate ((CO3)2-) is 289.3 +/- 0.6 eV (average of 18 carbonates, + 4.5 eV above adventitious carbon at 284.8 eV). Calcium carbonate is at 289.5 eV +/-0.1 eV or + 4.7 eV above adventitious carbon). Note thate silver carbonate has a much lower binding energy at ~288.5 eV.