Question

The shape of ammonia molecules is:

• A. Tetrahedral
• B. Trigonal pyramidal
• C. Trigonal bipyramidal
• D. Trigonal planar

Answer 1

The correct option is B

Trigonal pyramidal

Explanation for correct option:

B. Trigonal pyramid

Ammonia:

• Ammonia is a chemical compound that is made up of nitrogen and hydrogen atoms.
• The chemical formula of ammonia is ${\mathrm{NH}}_3$.

• The ammonia molecule has a trigonal pyramidal shape with the three hydrogen atoms and an unshared pair of electrons attached to the nitrogen atom.

The calculation for Hybridization of ${\mathrm{NH}}_3$:

• $$\begin{gathered} \mathrm{Steric}\mathrm{number}=\frac{1}{2}\left[\mathrm{V}+\mathrm{M}-\mathrm{C}+\mathrm{A}\right] \\ \mathrm{Steric}\mathrm{number}=\frac{1}{2}\times \left(5+3\right)=\frac{1}{2}\times 8 \\ \mathrm{Steric}\mathrm{number}=4 \end{gathered}$$
• Where V is the number of valence electrons of Nitrogen, M is the monovalent electron i.e. Hydrogen, C is the positive charge and A represents the negative charge( For ammonia there is no charge).
• Since the steric number of 4. Thus, the hybridization of ammonia molecules is ${\mathrm{sp}}^3$.

Explanation for incorrect options:

The shape of the ammonia molecule is trigonal pyramidal. Thus options A, C, and D are incorrect.

Hence, the correct option is B i.e. trigonal pyramid.