Lewis structure of Nitrogen trichloride (NCl3) molecule contains three sigma bonds and one lone pair around nitrogen atom. Therefore, there are total of four electrons regions around nitrogen atom which is important to decide geometry, shape and hybridization of a molecule. So, hybridization of phosphorus atom is sp3. Because there are four electrons regions, geometry is tetrahedral and shape is trigonal pyramidal.
To decide the geometry, shape and hybridization of a NCl33 molecule, drawing the correct lewis structure is very important.
Total electron region is taken by the summation of sigma bonds and lone pairs around nitrogen atom.
According to the lewis structure given above, there are three sigma bonds and one lone pair around the phosphorus atom. Therefore, total number of electron regions around nitrogen atom is four.
You can decide geometry and shapes of molecules from following table according to the number of electron regions.
Because, number of electron regions around nitrogen atom is four according to the lewis structure, geometry around nitrogen atom should be tetrahedral.
Because, there are three sigma bonds and one lone pair around nitrogen atom, molecular shape of phosphine is trigonal pyramidal.
Hybridization is also decided by the number of electron regions around an atom. A reference table is given below for identifying hybridization.
Because number of electron regions around phosphorus atom is four, hybridization of nitrogen trichloride atom is sp3
Questions
Nitrogen trichloride is very much similar to nitrogen trifloride considering both center atom and outside atoms because both outside atoms have three lone pairs in their valence shells. However, if only center atoms of molecules are considered, ammonia also has similar geometry, shape and hybridization to nitrogen trichloride molecule.