Question

Which one of the following is not paramagnetic?

• A. NO
• B. $N_2^+$
• C. CO
• D. $O_2^-$

Answer 1

The Correct Option is C

The question asks which of the given species is not paramagnetic. Paramagnetism is a property of substances that have unpaired electrons, resulting in a net magnetic moment. Let's analyze each option to determine their magnetic properties:

1. NO (Nitric Oxide): Nitric oxide has an odd number of electrons. The molecular orbital configuration of NO reveals that it has one unpaired electron, making it paramagnetic.
2. N_2^+ (Nitrogen Cation): This ion is formed by removing one electron from the nitrogen molecule N_2. The electronic configuration changes, and its molecular orbital diagram shows that it has an unpaired electron, making N_2^+ paramagnetic.
3. CO (Carbon Monoxide): CO is a diatomic molecule similar in structure to nitrogen (N_2). It has a complete set of bonding electron pairs and no unpaired electrons, which makes it diamagnetic.
4. O_2^– (Superoxide Ion): The superoxide ion has an extra electron compared to O_2. Its molecular orbital configuration includes an unpaired electron, making O_2^– paramagnetic.

Based on this analysis, the only option that is not paramagnetic is CO, as it has no unpaired electrons. Therefore, CO is diamagnetic.