CBSE Class 11-science Answered

Formation of PCl5 (sp3d Hybridisation)

• The ground state and the excited state outer electronic configurations of phosphorus (Z = 15) are given below:

• The formation of five half-filled sp3d hybrid orbitals involves the intermixing of one 3s, three 3p and one 3d orbitals during excitation.
• They are then organised in a trigonal bipyramidal symmetry. While three orbitals are organised in trigonal planar symmetry, the remaining two are kept perpendicularly above and below this plane.
• These half-filled sp3d orbitals help phosphorus in forming five σsp3d-p bonds with chlorine atoms. Each chlorine atom makes use of half-filled 3pz orbital for the bond formation.
• The PCl5 molecule has a trigonal bipyramidal shape with 120° and 90° of ∠Cl–P–Cl bond angles.