Question

why does oxygen exist as a diatomic molecule and sulpher a polyatomic molecule at room temperature

Answer 1

O2,SUPHUR ARE group 16 elements . They are collectively called as chalcogens (i.e ore forming substances ) since they are present along with ores ,except oxygen all the other four elements are solids at room temperature，so SULPHUR IS A POLYATOMIC atoms. Whereas oxygen is a gas and as gases always exist as diatomic molecules, oxygen is the only group 16 element which exists as diatomic molecule.