Si (atomic No. =14)
Ground state = 1s2 2s2 2p6 3s2 3px1 3py1 3pz0
Hybridized state = 1s2 2s2 2p6 3s1 3px1 3py1 3pz1
one e- is promoted from 4s to 3pz to produce 4 unpaired e- available for making bonds.
4 e - are shared by 4 H atoms to form SiH4.
Which orbitals are used in forming SiH4 ?
1s and 3p , (1e from 3s and 3 e- from 3p)
Therefore type of hybridization is sp3.