Why is the bond angle in an amide ion smaller than the bond angle in a molecule of ammonia?
The nitrogen atom in both NH3 and NH2- has 8 outer shell electrons. In NH3, 3 pairs of these electrons are used in covalent bonding to hydrogen atoms and the remaining 2 electrons exist as a lone pair. In NH2, there are 2 lone pairs of electrons due to there only being 2 hydrogen atoms involved in covalent bonding. Lone pairs create a stronger repulsion than bonding pairs. This results in a smaller bond angle in the amide ion due to the increased repulsion due to the extra lone pair. The repulsive force pushes the covalent bonds closer together.
