Describe the hybridisation in case of PCl5. Why are the axial bonds longer as compared to equatorial bonds?
The ground state and excited state outer electronic configurations of phosphorus (Z = 15) are:
Phosphorus atom is sp3d hybridized in the excited state. These orbitals are filled by the electron pairs donated by five Cl atoms as:
The five sp3d hybrid orbitals are directed towards the five corners of the trigonal bipyramidals. Hence, the geometry of PCl5 can be represented as:
The ground state E.C. and the excited state E.C. of phosphorus are represented as:
The one s, three-p and one d-orbitals hybridise to yield five sets of SP3 d hybrid orbitals which are directed towards the five corners of a trigonal bipyramidal as in Fig.
figure Trigonal bipyramidal geometry of PCl5 molecule
Because axial bond pairs suffer more repulsive interaction from the equatorial bond pairs, therefore axial bonds have been found to be slightly longer and hence slightly weaker than equatorial bonds.
Video Tutorials For All Subjects
- Hybridisation - Hybridisation - Introduction