# Carbonate Ion and it's structure

I recently began learning about resonance in molecules-

I drew the following Lewis dot structure for $$\ce{CO^{2-}_3}$$ ion and accounted for resonance in it.

Now I was asked about hybridisation and bond order of $$\ce{O}$$ in carbonate ion.

I thought that it will definitely not be $$\ce{sp^3}$$ and $$\ce{sp^2}$$ as indicated in Lewis dot structure of it because actual structure of carbonate is hybrid of above structures.

I started by treating each oxygen $$\ce{sp^2}$$ hybridised. Now all of them have unhybridised $$p$$ orbital perpendicular to the monitor screen and their sigma bonds are accounted by $$\ce{sp^2}$$ orbitals. The four parallel $$p-$$ orbitals form the base for conjugated $$\pi$$ system containing 6 electrons.

But the answer to the question was two oxygen have bond order 1 and $$\ce{sp^3}$$ hybridisation and remaining one has bond order 2 and $$\ce{sp^2}$$ hybridisation which is not correct I think.

Can you please correct me if I'm wrong?

• You are right. All oxygens are equivalent. If the answer says otherwise, it is intended for those who don't know about resonance. Jul 31 at 8:04
• And if you dig a bit further, surprise, all these oxygens are actual sp! Jul 31 at 11:31
• @Mithoron I actually dig a bit further but this chem.libretexts.org/Courses/can/org/… site says it to be sp2 only Jul 31 at 13:42
• @Mithorn I also found this answer chemistry.stackexchange.com/questions/21856/… Jul 31 at 13:52
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