Question

Why is dioxygen a gas but sulphur a solid?

Answer 1

1. Due to the small size and high electronegativity, oxygen forms pπ-pπ multiple bonds. As a result, oxygen exists as diatomic (O₂) molecules.
2. These molecules are held together by weak van der Waal’s forces of attraction, which can be overcome by collisions of the molecules at room temperature.
3. Therefore, O₂ is a gas at room temperature. Due to its bigger size and lower electronegativity, sulphur does not form pn-pn multiple bonds.
4. It prefers to form S-S single bonds. The S-S single bond is stronger than the O-O single bond. Thus, sulphur has a higher tendency for catenation than oxygen.
5. Due to a higher tendency for catenation and a lower tendency for pπ-pπ multiple bonds, sulphur exists as an octa-atomic (S₈) molecule.
6. Due to the bigger size, the force of attraction holding the S₈ molecules together is much stronger, which cannot be overcome by collisions of molecules at room temperature.

Therefore, sulphur is solid at room temperature.