Chapter 12, Problem 40A

Interpretation Introduction

Interpretation:

The geometric structure of ammonia is to be drawn and the bond angle is to be written.

Concept introduction:

The structure of a molecule can be drawn using the VSEPR theory. The total number of bonding and nonbonding pairs of electrons tells about the geometry of the molecule.

The valence electrons are the electrons present in the outermost shell.

Answer to Problem 40A

The geometric structure is tetrahedral.

4 pairs of electrons are surrounding the nitrogen in ammonia.

The approximate bond angle of $\mathrm{H}-\mathrm{N}-\mathrm{H}$ is $107\text{'}$ .

Explanation of Solution

Lewis structure of $\mathrm{N}{\mathrm{H}}_3$ is:

Structure shows in $\mathrm{N}{\mathrm{H}}_3$ central atom nitrogen have three bond pairs and one lone pair. In total, it has 4 pairs of electrons. Thus, its geometry is tetrahedral. But due to the presence of lone pair of electrons, its structure gets distorted and its shape is pyramidal according to VSEPR theory.

Thus, 4 pairs of electrons are surrounding the nitrogen in ammonia.

A normal tetrahedral bond has a bond angle of $109\text{'}28\text{'}\text{'}$ but due to the presence of a lone pair bond, the angle is reduced to $107\text{'}$ .

Conclusion

Thus, ammonia has a pyramidal shape due to the presence of a lone pair.