2023 Chemical Bonding and Molecular StructureMolecular Orbital Theory Medium Question 2 of 20 in Molecular Orbital Theory

The correct order of energies of molecular orbitals of $N_2$ molecule is:

A $\sigma1s<\sigma^*1s<\sigma2s<\sigma^*2s<(\pi2p_x=\pi2p_y)<(\pi^*2p_x=\pi^*2p_y)<\sigma2p_z<\sigma^*2p_z$
B $\sigma1s<\sigma^*1s<\sigma2s<\sigma^*2s<(\pi2p_x=\pi2p_y)<\sigma2p_z<(\pi^*2p_x=\pi^*2p_y)<\sigma^*2p_z$
C $\sigma1s<\sigma^*1s<\sigma2s<\sigma^*2s<\sigma2p_z<(\pi2p_x=\pi2p_y)<(\pi^*2p_x=\pi^*2p_y)<\sigma^*2p_z$
D $\sigma1s<\sigma^*1s<\sigma2s<\sigma^*2s<\sigma2p_z<\sigma^*2p_z<(\pi2p_x=\pi2p_y)<(\pi^*2p_x=\pi^*2p_y)$

The answer is B.

Solution

For $N_2$ (fewer than 15 electrons) the $\pi2p$ orbitals lie below $\sigma2p_z$.

$\sigma1s<\sigma^*1s<\sigma2s<\sigma^*2s<(\pi2p_x=\pi2p_y)<\sigma2p_z<(\pi^*2p_x=\pi^*2p_y)<\sigma^*2p_z$ is the correct order of energy of MO for homo nuclear diatomic species $N_2$.

Concept MO energy order of N2

Molecular Orbital Theory in past papers

20 questions from this chapter have appeared across 13 exam years.