AIEEE 2002 Chemistry Solved Paper

Bond angle 109∘28′ means Regular Tetrahedral geometry and hybridization is sp3 .
Steric Number (SN) for sp3 hybridization is 4.
In sp3 molecules can have different shapes which is decided by SN number
(1) 4 bond pair in a molecule then angle between bonds 109∘28′
(2) 3 bond pair and 1 lone pair in a molecule then angle between bonds 107∘ .
(3) 2 bond pair and 2 lone pair in a molecule then angle between bonds 104.5∘
(4) 1 bond pair and 3 lone pair in a molecule then bond angle is undefined as there is only one bond.
(1) In NH3,3 Bond pair(BP) +1 lone pair (LP) present so angle between bond 107∘.(2) BF4−,4 bond pair present so angle is 109∘28′.(3) In‌NH4+ , 4 bond pair present so angle between bond is 109∘28′(4) BF3 has sp2 hybridization. So bond angle is 120∘(5) In NH2−,2 bond pair and 2 lone pair present, so bond angle is 104.5∘