Question

ammonia, nh₃, adopts a tetrahedral geometry. however, the non-bonding pair on the central nitrogen atom distorts the bond angle away from the expected 109.5°. which of the following statements correctly describes how the bond angle is distorted?

the actual bond angle is reduced: it is less than 109.5°.

the actual bond angle is increased: it is more than 109.5°.

Explanation:

In ammonia ($\ce{NH_3}$), the central nitrogen atom has a lone (non - bonding) pair of electrons. Lone pairs exert a greater repulsive force than bonding pairs. In a tetrahedral electron - pair geometry (with one lone pair and three bonding pairs), the lone pair - bonding pair repulsions are stronger than bonding pair - bonding pair repulsions. This causes the bonding pairs to be pushed closer together, reducing the bond angle from the ideal tetrahedral angle of $109.5^{\circ}$. So the correct statement is that the actual bond angle is reduced (less than $109.5^{\circ}$).

Answer:

The actual bond angle is reduced: it is less than $109.5^{\circ}$