Using the molecular orbital diagram for diatomic molecules, which of the following species is paramagnetic?

• A. N_2
• B. F_2
• C. CO
• D. O_2

Answer: (D)

Verified step by step guidance

1. Recall that a species is paramagnetic if it has one or more unpaired electrons in its molecular orbitals.
2. Use the molecular orbital (MO) diagram for diatomic molecules to determine the electron configuration for each species: \(\mathrm{N_2}\), \(\mathrm{F_2}\), \(\mathrm{CO}\), and \(\mathrm{O_2}\).
3. Fill the molecular orbitals with the total number of valence electrons for each molecule, following the order of energy levels in the MO diagram (for example, \(\sigma_{2s}\), \(\sigma^*_{2s}\), \(\pi_{2p}\), \(\sigma_{2p}\), \(\pi^*_{2p}\), \(\sigma^*_{2p}\)).
4. Check for unpaired electrons in the highest occupied molecular orbitals (HOMOs) of each species. If there are unpaired electrons, the species is paramagnetic; if all electrons are paired, it is diamagnetic.
5. Identify that \(\mathrm{O_2}\) has two unpaired electrons in its \(\pi^*_{2p}\) orbitals, making it paramagnetic, while \(\mathrm{N_2}\), \(\mathrm{F_2}\), and \(\mathrm{CO}\) have all paired electrons and are diamagnetic.