1. In
H2S molecule, central atom
S is a 3rd period element and according to Dragos rule, when a 3rd period or higher period element overlap with a small element whose electronegetivity is low then that over lapping cannot be a effectiveoverlapping, because of higher size of 3rd or higher periods element and smaller size of low electronegative element.
Here in
H2S,H atom has very low electronegativity and smaller in size so it create more negative charge around sulphur(S) atom and size of
S−2 ion increases, because of this higher size difference efficiency overlapping isnot possible. So, any hybridization do not happen in between
S and
H atom. Lone pair electrons of
S atom is present in the pure orbital like
s,px,py ,
pz and it look like this :
As we know the angle between and
py is
90∘ , so bond angle is
90∘. 2. In
NH3,3 Bond pair(BP)
+1 lone pair (LP) present so angle between bond
107∘ .
3.
BF3 has
sp2 hybridization. So bond angle is
120∘ .
4.
Here
Si is
sp3 hybridised and shape is regular tetrahedral and bond angle
109∘28′