Question

Which of the following oxides is paramagnetic?

• A. SO$_2$
• B. NO$_2$
• C. SiO$_2$
• D. CO$_2$

Hint:

Odd-electron molecules are usually paramagnetic: \begin{itemize} \item NO, NO$_2$, ClO$_2$ \end{itemize} Even-electron molecules are typically diamagnetic.

Answer 1

The Correct Option is B

Concept: Paramagnetism arises due to presence of unpaired electrons. Step 1: Check electronic nature \begin{itemize} \item SO$_2$: all electrons paired $\Rightarrow$ diamagnetic \item NO$_2$: odd electron molecule $\Rightarrow$ one unpaired electron \item SiO$_2$: network covalent, diamagnetic \item CO$_2$: linear, all paired electrons \end{itemize} Conclusion: NO$_2$ contains an unpaired electron $\Rightarrow$ paramagnetic.