Which of the following species will be diamagnetic?

• A. O_2^{2-}
• B. O_2
• C. C_2
• D. B_2

Answer: (A)

Verified step by step guidance

1. Recall that a diamagnetic species has all its electrons paired, meaning there are no unpaired electrons in its molecular orbital configuration.
2. Write the molecular orbital (MO) electron configuration for each species using the appropriate MO energy ordering for diatomic molecules, especially for molecules with atomic numbers less than or equal to 14 (like B_2, C_2, O_2, and O_2^{2-}).
3. For O_2 and O_2^{2-}, use the MO diagram where the order of orbitals is: \(\sigma_{2s}\), \(\sigma_{2s}^*\), \(\sigma_{2p_z}\), \(\pi_{2p_x} = \pi_{2p_y}\), \(\pi_{2p_x}^* = \pi_{2p_y}^*\), \(\sigma_{2p_z}^*\).
4. Count the total number of electrons for each species (considering charges), fill the molecular orbitals accordingly, and determine if there are any unpaired electrons.
5. Identify which species has all electrons paired (no unpaired electrons) and is therefore diamagnetic.