Question

Assertion :Nitrogen does not form $NC{I}_5$ or $N{F}_5$ but phosphorus can. Reason: Nitrogen ($1s^{2}2s^{2}2p^3$) lacks 2d-orbitals in which electrons of 2s can be excited to make five orbitals unpaired. Only three electrons remain unpaired hence only $N{X}_3$ is formed. In case of $P\left(1s^{2}2s^{2}2p^{6}3s^{2}3p^3\right),3s$ electron can be excited into 3d vacant orbitals thus making five unpaired electrons, thus $P{X}_5$ is possible.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
• C. Assertion is correct but Reason is incorrect.
• D. Both Assertion and Reason are incorrect.

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.

As we know, P contains vacant d-orbitals whereas N having only two energy levels doesn't have vacant d-orbitals(for principal quantum number n=2, azimuthal quantum number l= 0,1 , i.e.,only the s and p orbitals.

Under excitation the valence electrons of P can jump to the vacant d-orbitals to form the oxidation state +5 and then form $PC{l}_5$ by $s{p}^{3}d$ hybridization. However, no vacant d-orbitals in N indicates that there is no scope of expanded octet nor the formation of $NC{l}_5$.