Which of the following oxides of nitrogen is paramagnetic and contains a nitrogen-nitrogen bond?

Solution

1. ${\text{N}}_2\text{O}$ is diamagnetic and has a linear structure.
2. ${\text{NO}}_2$ has 17 valence electrons, making it an odd-electron molecule that is paramagnetic.
3. ${\text{N}}_2{\text{O}}_4$ and ${\text{N}}_2{\text{O}}_3$ are diamagnetic as they have paired electrons.
4. Hence the answer is (B).