Describe hybridisation in the case of `PCl_(5) and SF_(5)` The axial bonds are longer as compared to rwuatorial bonds in `PCl_(5)` whereas in `SF_(6)` both axial bonds and equatorial bonds and have the same bond length. Explain.

Explanation

Formation of `PCl_(5)`

In `PCl_(5)`, phosphorous is `sp^(3)d` hybridised to produce a set of five `sp^(3)d` hybrid orbitals which are directed towards the five corners of a triagoal bipyramidal. These five `sp^(3)d` hybrid orbitals overlap with singly occupied p-orbitals of Cl-atoms to form five P-Cl sigma bonds.

Three P-Cl bonds lie in one plane and make an angle of `120^(@)` with each other. These bonds are called equatorial bonds. The remaining two P-Cl bonds one lying above and other lying below the plance make an angle of `90^(@)` with the equotorial plane.
These bonds are called axial bonds. Axial bonds are slightly longer than equatorial bonds bcecause axial bonds pairs under more repulsive inetraction from the equatorial bond pairs.
Formation of `SF_(6)`

In `SF_(6)`, sulphur is `sp^(3)d^(2)` hybridised to produce a set of six `sp^(3)d^(2)` hyrbrid which are directed towards the six corner of a regular octahedron. These six `sp^(3)d^(2)` hyrbid orbitals overlap with singly occupied orbitals of fluorine atoms to form six S-F sigma bonds.
Thus, `SF_(6)` molecule has a regular octahedral geometry and all S-F bonds have same bond length.