Question

Pcl5 is known but Ncl5 is unknown why

Answer 1

PCl5 forms five bonds by using the d-orbitals to "expand the octet" and have more "places" to put bonding pairs of electrons. NCl5 does not exist because there are no d-orbitals in the second energy level. Therefore there is no way to arrange five pairs of bonding electrons around a nitrogen atom.

Answer 2

Phosphorous has d-orbitals & hence

can accommodate the electrons

from Cl into them,in case of N the

d-orbitals are absent & electrons can be

accommodated only in p-orbitals.Hence

PC15 exists.