Which statement is true about the energy levels of bonding and antibonding molecular orbitals?

• A. Bonding and antibonding molecular orbitals have the same energy.
• B. Bonding molecular orbitals have lower energy than antibonding molecular orbitals.
• C. Antibonding molecular orbitals are always occupied before bonding molecular orbitals.
• D. Bonding molecular orbitals have higher energy than antibonding molecular orbitals.

Answer: (B)

Verified step by step guidance

1. Understand that molecular orbitals are formed by the combination of atomic orbitals when atoms bond together.
2. Recognize that bonding molecular orbitals result from constructive interference of atomic orbitals, which leads to increased electron density between nuclei and thus lower energy.
3. Know that antibonding molecular orbitals result from destructive interference, causing a node between nuclei and higher energy compared to bonding orbitals.
4. Recall that electrons fill molecular orbitals starting from the lowest energy level, so bonding orbitals are filled before antibonding orbitals.
5. Conclude that bonding molecular orbitals have lower energy than antibonding molecular orbitals, making the statement 'Bonding molecular orbitals have lower energy than antibonding molecular orbitals' true.