In which of the following molecules/ions $\mathrm{BF}_3, \mathrm{NO}_2^{-}, \mathrm{NH}_2^{-}$and $\mathrm{H}_2 \mathrm{O}$, the central atom is $\mathrm{sp}^2$ hybridised ?

• A

  $\mathrm{NO}_2^{-}$and $\mathrm{NH}_2^{-}$
• B

  $\mathrm{NH}_2^{-}$and $\mathrm{H}_2 \mathrm{O}$
• C

  $\mathrm{NO}_2^{-}$and $\mathrm{H}_2 \mathrm{O}$
• Correct answer
  D

  $\mathrm{BF}_3$ and $\mathrm{NO}_2^{-}$

Solution

Key Idea For $\mathrm{sp}^2$ hybridisation, there must be either $3 \sigma$ bonds or $2 \sigma$ bonds and one lone pair of electrons in the molecule or ions.



Thus, in $\mathrm{BF}_3$ and $\mathrm{NO}_2^{-}$, central atom is $\mathrm{sp}^2$ hybridised.

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