In aqueous solution the amide ion, NH₂⁻, is protonated to form ammonia, NH₃. The transformation alters both the number of lone pairs on nitrogen and the overall charge on the species.
Analyze how this acid–base reaction affects the H–N–H bond angle.
(1) For both NH₂⁻ and NH₃, state the steric number and hybridization of the nitrogen atom.
(2) Predict whether the H–N–H bond angle increases, decreases, or remains unchanged upon protonation. Support your prediction with a quantitative estimate (±2°) for the bond angle in each species.
(3) Provide a chemical rationale for the change you predicted in part (b), discussing (i) differences in lone-pair–bonding-pair repulsions, (ii) the effect of formal charge on electron-pair distribution, and (iii) any consequences for the effectiveness of orbital hybridization.