First draw the Lewis Structure of so2.
Note that there are 3 things or regions around the central atom. 1 single bond 1 double bond and a lone pair.
The hybridization for this is sp2
Where:
s has 1 orbital
p has 3 orbitals
d has 5 orbitals
f has 7 orbitals
sp2 s has 1 orbital p has 2 orbitals = 3 regions
Let’s say you have 4 things or regions around the central atom like nh3
The hybridization for this is sp3
sp3 s has 1 orbital p has 3 orbitals = 4 regions
Let’s look at PCL5. It has 5 things or regions around the central atom.
The hybridization for this is sp3d
sp3 s has 1 orbital p has 3 orbitals d has 1 orbital = 5 regions
We can’t have more than 3 orbitals on p so that’s why we jumped to d orbital.
Don’t forget to check this also