In the reaction 2PCl5 ⇌PCl4+ + PCl6–   the change in hybridization is from

Number of electron pairs = V = Group number of central atomM = Number of monovalent groups directly attached to central atomC = overall positive  charge of the speciesA = Overall negative charge of the species.Number of bond pairs = Number of atoms directly attached to central atom"Bond Pairs" according to VSEPR theory can be single bond, double b and (or) triple bondNumber of lone pairs = (Number of electron pairs-Number of bond pairs)