Question

Which of the following molecules has a trigonal pyramidal geometry?

• A. $B{H}_3$
• B. $H_{2}O$
• C. $C{H}_4$
• D. $N{H}_3$
• E. $AlC{l}_3$

Answer 1

The correct option is D $N{H}_3$

Option $D$ is the correct answer.

${NH}_3$ has trigonal pyramidal geometry. Nitrogen has five electrons in its outermost shell. Of them, three are required to form three sigma bonds with three Hydrogen atoms. One lone pair still remains on the NItrogen atom. Thus, ${NH}_3$ is ${sp}^3$ hybridized and should have an angle of about ${109}^o$ . But because of the presence of one lone pair on Nitrogen atom, its bond angle decreases to about ${107}^o$.