ClO4- - Perchlorate ionNo of electron pairs = 1/2 [V + M - C + A]V = No of valency electronsM = No of monovalent atoms bonded to central atomC = Total charge on cationA = Total charge on anionClO4- :-No of electron pairs = 1/2 [7 + 0 - 0 + 1]No of electron pairs= 8/2 = 4 ⇒ sp3 - hybridisation :. Cl in ClO4- uses sp3 hybrid orbitals.             [OR]          ClO4-                                   Each cross [x] indicates one electron of valency shell of chlorine