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NEET CHEMISTRYMedium

The correct order of energies of molecular orbitals of N2_2 molecule is:

A

σ1s<σ∗1s<σ2s<σ∗2s<(π2px=π2py)<σ2pz<(π∗2px=π∗2py)<σ∗2pz\sigma 1s < \sigma^* 1s < \sigma 2s < \sigma^* 2s < (\pi 2p_x = \pi 2p_y) < \sigma 2p_z < (\pi^* 2p_x = \pi^* 2p_y) < \sigma^* 2p_z

B

σ1s<σ∗1s<σ2s<σ∗2s<σ2pz<(π2px=π2py)<(π∗2px=π∗2py)<σ∗2pz\sigma 1s < \sigma^* 1s < \sigma 2s < \sigma^* 2s < \sigma 2p_z < (\pi 2p_x = \pi 2p_y) < (\pi^* 2p_x = \pi^* 2p_y) < \sigma^* 2p_z

C

σ1s<σ∗1s<σ2s<σ∗2s<σ2pz<(π2px=π2py)<(π∗2px=π∗2py)<σ∗2pz\sigma 1s < \sigma^* 1s < \sigma 2s < \sigma^* 2s < \sigma 2p_z < (\pi 2p_x = \pi 2p_y) < (\pi^* 2p_x = \pi^* 2p_y) < \sigma^* 2p_z

D

σ1s<σ∗1s<σ2s<σ∗2s<σ2pz<(π2px=π2py)<σ∗2pz<(π∗2px=π∗2py)\sigma 1s < \sigma^* 1s < \sigma 2s < \sigma^* 2s < \sigma 2p_z < (\pi 2p_x = \pi 2p_y) < \sigma^* 2p_z < (\pi^* 2p_x = \pi^* 2p_y)

Step-by-Step Solution

  1. General Rule: For homonuclear diatomic molecules of the second period, the order of molecular orbital energies depends on the number of electrons.
  2. Molecules with Z > 7 (O2{_2}, F2{_2}, Ne2{_2}): The energy of the σ2pz\sigma 2p_z orbital is lower than that of the π2px\pi 2p_x and π2py\pi 2p_y orbitals .
  3. Molecules with Z ≤\le 7 (Li2{_2}, Be2{_2}, B2{_2}, C2{_2}, N2{_2}): Experimental observations show a different order due to the mixing of 2s and 2p orbitals (s-p mixing). In these cases, the energy of the σ2pz\sigma 2p_z orbital is higher than that of the π2px\pi 2p_x and π2py\pi 2p_y orbitals .
  4. Specific Order for N2{_2}: The increasing order of energies is: σ1s<σ∗1s<σ2s<σ∗2s<(π2px=π2py)<σ2pz<(π∗2px=π∗2py)<σ∗2pz\sigma 1s < \sigma^* 1s < \sigma 2s < \sigma^* 2s < (\pi 2p_x = \pi 2p_y) < \sigma 2p_z < (\pi^* 2p_x = \pi^* 2p_y) < \sigma^* 2p_z This corresponds to Option A.
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