In case of Nitrogen, NCl3 is possible but not NCl5, whereas in case of P, PCl3 as well as PCl5 is possible, this is because:
1
Availability of vacant d orbital in P but not in N.
2
Lower electronegativity of P than N.
3
Lower tendency of H bond formation in P than N.
4
Occurrence of P in solid state while N in gaseous state at room temperature.