JEE Chemistry 2025 Question with Solution

Given: Oxygen and sulphur show a large difference between their melting and boiling points.

Find: The basis on which this difference is explained.

From the solution, oxygen exists as $O_2$ while sulphur exists as $S_8$. This means their atomicity is different.

Sulphur as $S_8$ has a larger and more complex molecular form, so the intermolecular van der Waals forces between sulphur molecules are stronger than those between $O_2$ molecules. Stronger intermolecular forces require more energy to overcome, so sulphur has much higher melting and boiling points.

Atomic size, electronegativity, and electron gain enthalpy do not primarily explain this large difference here.

Therefore, the correct option is B, Atomicity.

Given: Oxygen and sulphur belong to the same group, but oxygen exists as $O_2$ and sulphur commonly exists as $S_8$.

Find: Which property explains the large difference in their melting and boiling points.

1. Atomicity: Atomicity means the number of atoms present in one molecule.
2. Oxygen is a diatomic molecule, $O_2$.
3. Sulphur is an octatomic molecule, $S_8$.
4. Because $S_8$ is much larger than $O_2$, sulphur molecules experience stronger intermolecular van der Waals forces.
5. Stronger intermolecular forces increase both melting point and boiling point.
6. Hence, the major reason for the large difference is atomicity.

The other options are not the main cause in this comparison.

Therefore, the correct option is B.