Question

Why is dioxygen a gas but sulphur a solid?

Answer 1

The O--O bond is weaker than the S--S bond due to greater inter-electronic repulsions in small sized oxygen atom moreover being smaller and highly electronegative oxygen forms $p\pi$-$p\pi$ multiple bonds. So, it exists as $O_2$ molecules which are held together by weak vander Waals' force. Thus oxygen exists as a gas at room temperature. sulphur has less tendency to form $p\pi$-$p\pi$ multiple bonds. moreover it has large atomic size, less electronegativity and forms strong S--S single bonds, that's why it shows more catenation property and exists as $S_8$ molecules having puckered ring structure. Hence, sulphur is a solid at room temperature.