Question

Why does oxygen not show oxidation states of +4 and +6, whereas sulphur does so?

Answer 1

1. Oxygen does not show +4 and +6 oxidation states because it lacks vacant d-orbitals in its valence shell, so it cannot excite paired electrons to higher states.
2. Sulphur and heavier group 16 elements have vacant d-orbitals, which allow excitation of electrons to these orbitals and formation of +4 and +6 states.
3. Oxygen usually shows −2 state due to its high electronegativity and the preference to gain or share two electrons.
4. Sulphur exhibits +2, +4, and +6 oxidation states through excitation and hybridisation involving d-orbitals (sp³d or sp³d²).

Thus, the presence or absence of vacant d-orbitals and electronegativity differences explain the oxidation state behaviour of oxygen and sulphur.