Identify the species having one π-bond and maximum number of canonical forms from the following:

Question

Canvas Classes · Accepted Answer

Step 1 — Count π bonds and canonical forms:

: Has 3 π bonds (resonance) and 3 canonical forms — but has 3 π bonds, not one.

: Has 1 π bond and only 1 canonical form (no resonance). ✗

: Has 1 π bond and 2 canonical forms. ✗

(carbonate ion): 
- Has 1 π bond (delocalized over 3 C–O bonds)
- Has 3 canonical/resonance forms (maximum among the options with 1 π bond)
- The π bond is delocalized, giving 3 equivalent resonance structures ✓

Step 2:  has 1 delocalized π bond and 3 canonical forms — m

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