According to Molecular Orbital Theory, for which of the following pairs of diatomic molecules is the energy of the _ 2p_z molecular orbital greater than that of the _ 2p_x and _ 2p_y molecular orbitals?

Step-by-step solution

In Molecular Orbital Theory, for homonuclear diatomic molecules up to N ₂ (i.e., having 14 or fewer electrons), the 2s - 2p mixing is significant. This causes the energy of the _ 2p_z orbital to rise above the energies of the _ 2p_x and _ 2p_y orbitals. Both N ₂ (14 electrons) and C ₂ (12 electrons) fall into this category. For molecules with more than 14 electrons, such as O ₂ (16 electrons) and F ₂ (18 electrons), the _ 2p_z orbital is lower in energy than the _ 2p_x and _ 2p_y orbitals. Answer: N ₂ and C ₂