Question

The decreasing values of bond angles from NH₃ (106°) to SbH₃ (101°) down group-15 of the periodic table is due to
(a) increasing bond-bond pair repulsion
(b) increasing p-orbital character in sp₃
(c) decreasing lone pair-bond pair repulsion
(d) decreasing electronegativity.

Answer 1

(c) :                  NH₃         PH₃     AsH₃    SbH₃ 

Bond angle    106.5°   93.5°   91.5°    91.3° 

The bond angle in ammonia is less than 109° 28' due to repulsion between lone pairs present on nitrogen atom and bonded pairs of electrons. As we move down the group, the bond angles gradually decrease due to decrease in bond pair lone pair repulsion.