JEE Chemistry 2024 Question with Solution

Step-by-step solution

Common mistakes

• Counting the total number of molecular orbitals instead of only the antibonding ones. This is wrong because the question specifically asks for antibonding molecular orbitals. First list all MOs, then count only those marked with $*$.

• Forgetting that the two $\pi^*$ orbitals are degenerate but still count as two separate orbitals. Degeneracy does not reduce the number of orbitals. Count both $\pi^*_{2p_x}$ and $\pi^*_{2p_y}$ separately.

• Ignoring the antibonding orbital from the $2s$ combination. This is wrong because combining two $2s$ atomic orbitals gives one bonding and one antibonding MO. Include $\sigma^*_{2s}$ in the count.