Which of the following is not a correct statement?

• A

  Multiple bonds are always shorter than corresponding single bonds
• B

  The electron deficient molecules can act as Lewis acids
• C

  The canonical structures have no real existence
• Correct answer
  D

  Every $\mathrm{AB}_5$ molecule does in fact have square pyramidal structure

Solution

The $\mathrm{AB}_5$ molecule does not have a square pyramidal structure but has a trigonal bipyramidal structure because of $s p^3 d$ hybridisation. Related Theory Benzene exist in canonical structure

Hence, the correct answer is option: 'D'.