Question

Why is dioxygen a gas but sulphur a solid?

Answer 1

Oxygen has small atomic size and high electronegativity. It forms $p\pi -p\pi$ double bonds, $O=O$. The inter-molecular forces are weak vander waals forces. Hence, oxygen is a gas. Whereas sulphur does not form stable $p\pi -p\pi$ bonds and does not exist as $S_2$ molecule. It forms $S_8$ molecules with puckered ring structure. Thus, each molecule contains $8S$ atoms linked by $S-S$ bonds. Thus, $S$ atoms are strongly held and sulphur is a solid.