Question

What are the resonance structures for `CO_3^-2`?

Answer 1

This is a carbonate ion. A resonance structure means that there are more than one way to draw the ion.

Explanation:

First, determine the total number of electrons available:

1 Carbon - 4
3 Oxygen - `6(3) = 18`

And the charge of `-2` gives you an additional 2 electrons.

Hence, there are 24 electrons in total (`4+18+2=24`)

Carbon would be in the middle which gives you

However, note that carbon does not have a full octet shell. Hence, a pair of electrons from oxygen needs to come over and form a double bond. Note that the double bond can come from any oxygen atom which gives carbonate its resonance structure.