JEE Chemistry 2025 Question with Solution

Given: The molecules listed are $\mathrm{O_2}$, $\mathrm{N_2}$, $\mathrm{F_2}$, $\mathrm{S_2}$ and $\mathrm{Cl_2}$.

Find: Which option corresponds to the paramagnetic molecules.

A molecule is paramagnetic if it contains unpaired electrons. Using molecular orbital theory:

• $\mathrm{O_2}$ has two unpaired electrons, so it is paramagnetic.
• $\mathrm{N_2}$ has all electrons paired, so it is diamagnetic.
• $\mathrm{F_2}$ has all electrons paired, so it is diamagnetic.
• $\mathrm{S_2}$ is analogous to $\mathrm{O_2}$ and has unpaired electrons, so it is paramagnetic.
• $\mathrm{Cl_2}$ has all electrons paired, so it is diamagnetic.

Therefore, the paramagnetic molecules are $\mathrm{O_2}$ and $\mathrm{S_2}$.

Among the given combined-answer options, this corresponds to (4) A & D only.

The correct option is A.

Note: The solution's states option D, but the solution working clearly concludes (4) A & D only. Hence the option list has been preserved verbatim and the answer has been derived from the solution content.

Given: Paramagnetism depends on the presence of unpaired electrons.

Find: Which listed molecules contain unpaired electrons.

A quick check gives:

• $\mathrm{O_2}$: $2$ unpaired electrons
• $\mathrm{N_2}$: $0$ unpaired electrons
• $\mathrm{F_2}$: $0$ unpaired electrons
• $\mathrm{S_2}$: $2$ unpaired electrons
• $\mathrm{Cl_2}$: $0$ unpaired electrons

So the paramagnetic molecules are $\mathrm{O_2}$ and $\mathrm{S_2}$ only, which matches (4) A & D only.

Therefore, the correct option is A.