Question

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

Answer 1

Oxygen differs from other elements of group 16 (S, Se, Te, Po) due to its small size, high electronegativity, and absence of vacant d-orbitals. Its anomalous behaviour is as follows:

• (i) Atomicity: Oxygen exists as a diatomic molecule (\(O_2\)), whereas other group members exist as polyatomic molecules such as \(S_8\), \(Se_8\), etc.
• (ii) Oxidation state: Oxygen shows only two common oxidation states: \(-2\) (in most compounds) and \(-1\) (in peroxides). Other group members exhibit higher oxidation states like \(+4\) and \(+6\) due to the presence of d-orbitals.
• (iii) Magnetic property: Dioxygen (\(O_2\)) is paramagnetic due to the presence of two unpaired electrons in antibonding molecular orbitals (\(\pi^*_{2p}\)). Other group members in molecular form are generally diamagnetic.
• (iv) Nature of hydrides: Water (\(H_2O\)) is a liquid at room temperature, has strong hydrogen bonding, and shows high boiling point. Hydrides of other group members (H\(_2\)S, H\(_2\)Se, H\(_2\)Te) are gases with weak intermolecular forces and much lower boiling points.

Final Answer:

Oxygen shows anomalous behaviour in all four aspects: It exists as diatomic \(O_2\), has limited oxidation states, is paramagnetic, and forms a unique hydrogen-bonded liquid hydride (water).