Question
In which of the following pairs of molecules/ions, the central atoms have $$s{p^2}$$ hybridisation?
A.
$$NO_2^ - \,{\text{and}}\,N{H_3}$$
B.
$$B{F_3}\,{\text{and}}\,NO_2^ - $$
C.
$$NH_2^ - \,{\text{and}}\,{H_2}O$$
D.
$$B{F_3}\,{\text{and}}\,NH_2^ - $$
Answer :
$$B{F_3}\,{\text{and}}\,NO_2^ - $$
Solution :
Key Idea For $$s{p^2}$$ hybridisation, there must be $$3\sigma - {\text{bonds}}\,\,{\text{or}}\,2\sigma - {\text{bonds}}\,$$ along with a lone pair of electrons.
$$\left( {\text{i}} \right)NO_2^ - \Rightarrow 2\sigma + 1\,lp = 3,$$ $${\text{i}}{\text{.e}}{\text{.}}\,s{p^2}\,\,{\text{hybridisation}}$$
$$\left( {{\text{ii}}} \right)N{H_3} \Rightarrow 3\sigma + 1\,lp = 4,$$ $${\text{i}}{\text{.e}}{\text{.}}\,s{p^3}\,\,{\text{hybridisation}}$$
$$\left( {{\text{iii}}} \right)B{F_3} \Rightarrow 3\sigma + 0\,lp = 3,$$ $${\text{i}}{\text{.e}}{\text{.}}\,s{p^2}\,\,{\text{hybridisation}}$$
$$\left( {{\text{iv}}} \right)NH_2^ - \Rightarrow 2\sigma + 2\,lp = 4,$$ $${\text{i}}{\text{.e}}{\text{.}}\,s{p^3}\,\,{\text{hybridisation}}$$
$$\left( {\text{v}} \right){H_2}O \Rightarrow 2\sigma + 2\,lp = 4,$$ $${\text{i}}{\text{.e}}{\text{.}}\,s{p^3}\,\,{\text{hybridisation}}$$
Thus, among the given pairs, only $$B{F_3}$$ and $$NO_2^ - $$ have $$s{p^2}$$ hybridisation.