Practice Problem

The chief resonance contributors (canonical forms) for the five compounds and ions are shown below. Other structures can be written, but they will be destabilized by reduced bonding and/or charge separation.
Considering the canonical forms written here, which three of these compounds or ions will exhibit the greatest resonance stabilization? Enter the numbers corresponding to the compound(s) you select in the answer box.

1. Formic Acid	HCO2H			Answer Box:
2. Formate Anion	HCO2(–)
3. Nitromethane	CH3NO2
4. Methyl Nitrite	CH3ON=O
5. Ozone	O3