Ozone, O3
Two contributors exchange the single and double O–O bonds. The central oxygen carries a positive formal charge in each contributor.
Open O3 guideDelocalized electron structures
Resonance Lewis Structure Examples
Resonance contributors keep the same atomic connectivity but move electrons, pi bonds or formal charges. The real molecule is not rapidly switching pictures; it is represented by a resonance hybrid.
Nitrate, NO3−
Three contributors place the N=O bond at three different oxygen atoms. The hybrid has equivalent N–O positions.
Open nitrate guideCarbonate, CO32−
Three contributors distribute the double bond and negative charges across the oxygen atoms.
Open carbonate guideNitrite, NO2−
Two contributors exchange the N=O position while the N–O framework remains bent.
Open nitrite guideSulfur dioxide, SO2
Different textbooks may emphasize charge-separated contributors or expanded-valence drawings. State the convention being used.
Open SO2 guideBenzene, C6H6
Two Kekulé contributors alternate the three pi bonds around an unchanged six-carbon ring.
Open benzene guideFour checks for valid contributors
- Keep the same atom connectivity.
Only electron placement changes.
- Keep the same total charge.
Every contributor represents the same species.
- Count the same total electrons.
No dots or bonds may appear from nowhere.
- Use formal charge to compare contributors.
Lower charge separation is often favored, subject to octet and electronegativity rules.