Question

pcl-5 exist but ncl-5 does not exist explain?

Answer 1

Answer:
The configuration of the external electrons of the atom phosphorus 1s22s22p63s23p3. Unlike nitrogen, phosphorus possesses free 3d orbitals with rather low energies, which leads to the possibility of increasing the coordination number and the formation of donor-acceptor bonds.
Therefore, phosphorus can form compounds PCl5 and nitrogen cannot form NCl5.