Here's why:
* Iron(III) (ferric) ions have a +3 charge (Fe³⁺).
* Carbonate ions have a -2 charge (CO₃²⁻).
To balance the charges, you would need two ferric ions and three carbonate ions, resulting in a formula of Fe₂(CO₃)₃. However, this compound is highly unstable and readily decomposes in water.
When exposed to water, ferric carbonate would decompose into iron(III) hydroxide (Fe(OH)₃) and carbon dioxide (CO₂):
Fe₂(CO₃)₃ + 3H₂O → 2Fe(OH)₃ + 3CO₂
Therefore, it is not accurate to refer to a stable compound as ferric carbonate.
