Question

PCl₅ exists but NCl₅ does not. Explain.

Answer 1

1. PCl₅ exists but NCl₅ does not because phosphorus can expand its octet by using vacant 3d orbitals, allowing it to form 5 bonds.
2. Nitrogen lacks vacant d orbitals (it is limited to 2p orbitals), so it cannot expand its octet to accommodate 5 bonds.
3. Without the ability to expand its octet, nitrogen cannot stabilize the required bonding for NCl₅.

Hence, NCl₅ is unstable and does not exist, whereas PCl₅ is stable and commonly found.