Question

\(PCl_5\) is well known, but \(NCl_5\) is not. Because,

• A. nitrogen is less reactive than phosphorous
• B. nitrogen doesn’t have d-orbitals in its valence shell.
• C. catenation tendency is weaker in nitrogen than phosphorous.
• D. size of phosphorous is larger than nitrogen

Answer 1

The Correct Option is B

To understand why \(NCl_5\) is not known while \(PCl_5\) is well known, we need to consider the electronic configurations and the availability of orbitals in the valence shell of nitrogen and phosphorus.

1. Electronic Configuration:
   • Nitrogen (\(N\)): The electronic configuration is \(1s^2 2s^2 2p^3\). The valence shell comprises 2s and 2p orbitals.
   • Phosphorus (\(P\)): The electronic configuration is \(1s^2 2s^2 2p^6 3s^2 3p^3\). In the valence shell, it has 3s, 3p, and access to 3d orbitals.
2. Valency and Orbital Availability:
   • Nitrogen does not have d-orbitals in its valence shell. Therefore, it cannot expand its octet to form compounds like \(NCl_5\). Typically, nitrogen can form three covalent bonds using its three unpaired p-orbitals (as in \(NH_3\)).
   • Phosphorus, on the other hand, has access to vacant d-orbitals, which allows it to expand its valency beyond 3 to 5. This enables phosphorus to form \(PCl_5\) by using the d-orbitals to accommodate five covalent bonds.
3. Conclusion: Based on the above explanation, the correct answer is: "nitrogen doesn’t have d-orbitals in its valence shell." This absence prevents nitrogen from forming \(NCl_5\).

Thus, phosphorus can participate in a greater range of chemical bonding due to the availability of d-orbitals compared to nitrogen, which is limited by not having such orbitals.