Isodesmic and Anisodesmic bonding: (carbonates & silicates)
Ca[CO₃^2-] radical
CO₃^2- (triangular)

• residual charge on each oxygen=-2/3 in the CO₃^2-
  
• 1 1/3 of a negative charge being contributed by each oxygen to the carbon, therefore oxygens contribute 2/3 of their charge to Ca
• bond of carbons to oxygen is stronger than bond of oxygen to Ca²⁺

anisodesmic: bond strength - uneven
-important in weathering

isodesmic: ^-4 charge must be satisfied by cations - tetrahedra link to form chains

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