Group 15 Halides Existence

$$\text{PCl}_5 \implies \text{Exists (sp}^3\text{d hybridization)}$$ 

$$\text{NCl}_5 \implies \text{Does Not Exist}$$

Concept: Phosphorus can expand its valence octet using vacant $$3d$$ -orbitals to form pentahalides, whereas nitrogen is restricted to a maximum covalency of four due to the absolute absence of low-energy valence $$d$$ -orbitals.

Notation:

• $$\text{PCl}_5$$ = Phosphorus pentachloride;
• $$\text{NCl}_5$$ = Non-existent nitrogen pentachloride.