Hybridization of central atom in NF3 is:

The general formula to find the type of hybridization in a given type of compounds is:X=12(V+M+A−C) where V=number of electronsin valence shell; M = number of monovalent atoms;A=charge on anion and C= charge on cation. Central atom, has 5(i.e. 2 of 2s+3 of 2p) valence electrons;no. of monovalent atoms in NF3=3. Thus ;x=12(5+3+0-0)=4.Hence, type of hybridization is sp3(∴1+3=4).