Question

$ PC{l_5} $ exists but $ NC{l_5} $ does not because:
(A) Nitrogen has no vacant 2d-orbital
(B) $ NC{l_5} $ is unstable.
(C) Nitrogen atom is much smaller than P
(D) Nitrogen is highly inert.

Answer 1

Hint: In order to solve this question we will learn the presence of no of electrons and the orbitals that are present in the P and N then according to this we will see the number of electrons that can filled in the phosphorus and in the orbitals of the nitrogen.

Complete answer:
For solving this question we will first learn the electronic configuration of both nitrogen and the phosphorus:
 $ N = 1{s^2}2{s^2}2{p^3} $
 $ p = 1{s^2}2{s^2}2{p^6}3{s^2}3{p^3} $
 $ PC{l_5} $ forms five bonds by using the d-orbitals to expand the octet" and have more places to put bonding pairs of electrons. $ PC{l_5} $ 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.
By the above discussion it is clear that the first option is correct.
Additional option:
Phosphorus pentachloride is the chemical compound with the formula $ PC{l_5} $ . It is one of the most important phosphorus chlorides, others being $ PC{l_3} $ and $ POC{l_3} $ . $ PC{l_5} $ finds use as a chlorinating reagent. It is a colourless, water-sensitive and moisture-sensitive solid, although commercial samples can be yellowish and contaminated with hydrogen chloride.

Note:
While solving these types of problems we should keep in mind that the d orbital starts from the third period, similarly f orbital starts from the fourth period. Rather than this we should keep in mind and apply the Aufbau rule correctly.