Oxygen is smaller in size as compared to sulphur. Due to its smaller size, it can effectively form pπ –pπ bonds and form O₂[ O = = O] molecule. Also, the intermolecular forces in oxygen are weak van der Wall’s, which cause it to exist as a gas.

On the other hand, sulphur does not form M₂ molecule but exists as a puckered structure held together by strong covalent bonds. Hence, it is a solid.