Question

Account for the following:

Tendency to show −2 oxidation state diminishes from sulphur to poloniuum in group 16.

Answer 1

1. Group 16 elements have valence electron configuration ns² np⁴ and need 2 electrons to complete their octet, favouring the −2 oxidation state by gaining 2 electrons.
2. From sulphur (S) to polonium (Po), the tendency to show −2 oxidation state diminishes.
3. This is because electronegativity decreases down the group, reducing their ability to gain electrons.
4. Oxygen is highly electronegative and strongly prefers −2 state, but heavier elements like polonium have lower electronegativity and do not easily form M²⁻ ions.
5. Polonium does not show −2 oxidation state at all.
6. A decrease in electron gain enthalpy and an increase in metallic character down the group also contribute to this trend.

Thus, the −2 oxidation state is common for S and Se but less favoured for Te and absent for Po.