Why is dioxygen a gas but sulphur a solid ?

Explanation

Due to small size and high electronegativity, oxygen atom forms pit-prt multiple bonds with another oxygen atom. As a result, oxygen exists as a diatomic molecules `O_2`. These molecules are held together by weak van der Waals. forces of attraction. Therefore, `O_2` is a gas at room temperature.
Sulphur, on the other hand, because of its bigger size and lower electronegativity, does not form `p pi - p pi ` multiple bonds. Instead, it forms S-S single bonds `S_8`molecules having eight-membered puckered ring structure. Because of bigger size of the forces of attraction holding the `S_8` molecules together are much stronger. Consequently, sulphur exists as a solid at room temperature.