Why is dioxygen a gas but sulphur a solid?

Explanation

Oxygen due to its small size and high electronegativity form `ppi-ppi` multiple bonds. Hence oxygen exists as a dietomic `(O_2)` molecule. These molecules are held together by weak van der waals forces of attraction which can be easily overcome by collision of the molecules at room temperature `O_2` is a gas at room temperature. On the other hand sulphur due to its large size and low electronegativity, do not form `ppi-ppi` multiple bonds. Instead it prefers to form `S-S` single bonds. Further , because of stronger `S-S` bond than `O-O` bond, sulphur has a much greater tendency for catenation and exists as `S_8` molecule. Due to large molecular mass of `S_8` unit, the van der Waals forces of attraction holding `S_8` molecules together is very large and sulphur exist as solid at room temperature.