Question

How many resonance structures are there for `CO_3^(2-`?

Answer 1

The answer is 3
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Explanation:

Let’s consider the Lewis structure of the carbonate ion, CO32‐
.  The correct Lewis structure for this ion
has one carbon‐oxygen double bond, and two carbon‐oxygen single bonds.  Each of the singly bonded
oxygen atoms bears a formal charge of  ‐1 and all other atoms are neutral.  But which of the three
oxygens forms the double bond?  Well, there are three possibilities

As in the example above, when more than one viable Lewis structure can be drawn the molecule or
ion is said to have resonance.   The individual Lewis structures are termed contributing resonance
structures.    Resonance is a common feature of many molecules and ions of interest in organic
chemistry.