I have a homework question that says:

Question

"Three resonance structures of the following anion are possible. One is given below, but it is incomplete. Complete the given structure by adding non-bonding electrons and formal charges. Draw the two remaining resonance structures, including non-bonding electrons and formal charges."

The molecule they give us looks like this (but in a skeletal structure):

O(-)-c--c-c--c-c
|
H

The (-) is the formal charge on O, the - means a single bond, and the -- is a double bond.

I know there must be lone pairs on the O to give it its negative formal charge, but since the structure is in bond-line form and it says it's missing pieces, do I assume the there are Hydrogens attached to each one of those carbons or are there supposed to be lone pairs?
If there is supposed to be lone pairs, that would make each carbon have a formal charge which I don't think would be right. But if there are Hydrogens attached, when I try to form resonance structures, I don't know where to move electrons without exceeding the atoms' octet.

Could anyone help me with how to draw a resonance structure for this molecule??

Thanks!

Answer 1

That H is supposed to be attached to the first Carbon, it just got shifted when I posted the question!