Write anomalous behaviour of oxygen with respect to :(i) Atomicity(ii) Oxidation state(iii) Magnetic property(iv) Nature of hydrides.

Answer: Oxygen differs from the other group 16 elements because of its small size, high electronegativity and absence of d orbitals.

1. Atomicity: Oxygen is diatomic (O₂), forming pπ–pπ double bonds; sulphur and the others are polyatomic (S₈, Se₈).
2. Oxidation state: Oxygen shows mainly −2 (and −1 in peroxides, +2 only in OF₂); it cannot show +4 or +6 because it has no d orbitals, whereas S, Se, Te show +2, +4 and +6.
3. Magnetic property: O₂ is paramagnetic (two unpaired electrons in antibonding π* orbitals); the other elements are diamagnetic.
4. Nature of hydrides: H₂O is a liquid due to intermolecular hydrogen bonding, while H₂S, H₂Se and H₂Te are gases.