Numerical answer · +4 / −1
The number of resonance structures of benzene (C₆H₆) is x.
Answer and solution
Answer 2
Solution
Chemistry ma’am · 4 steps
Three double bonds can be placed around the ring in exactly two alternating ways.
- Count the pi electrons. Benzene, C₆H₆, has six π electrons, one on each carbon. They must be arranged as three π bonds.
- Place the double bonds. Draw alternating double and single bonds. You can start the first double bond at C1–C2 or at C2–C3. These are the only two arrangements that keep every carbon tetravalent.
- Why not more. Resonance structures change only the positions of π electrons, not the atoms or σ bonds. Any other drawing would change which carbons are bonded, making it a different molecule.
- So. There are exactly 2 resonance structures, so x = 2.
The common slip. Counting the resonance hybrid as a third structure gives 3. The hybrid is not a resonance structure; it is the average of the two.
The idea to keep. Resonance structures keep the same atoms and same sigma bonds; only pi electrons move. For benzene, that gives the two Kekulé structures.
Answer from the NTA final answer key. Solution by PrepWiser.