Question

How is the variability in oxidation states of transition metals different from that of the non-transition metals? Illustrate with examples.

How is the variability in oxidation states of transition metals different from that of the p-block elements?

Answer 1

In transition elements, the oxidation state can vary from +1 to the highest oxidation state by removing all its valence electrons. Also, in transition elements, the oxidation states differ by 1 (Fe²⁺ and Fe³⁺; Cu⁺ and Cu²⁺). In non-transition elements, the oxidation states differ by 2, for example, +2 and +4 or +3 and +5, etc.

Answer 2

The variability of oxidation states, a characteristic of transition elements, arises due to incomplete filling of d-orbitals in such a way that their oxidation states differ from each other by unity, e.g., Fe²⁺, Fe³⁺, Cr²⁺, Cr³⁺. This is in contrast with the variability of oxidation states of non-transition elements where oxidation states normally differ by a unit of two. i.e., Sn²⁺, Sn⁴⁺, P³⁺ and P⁵⁺, etc. in the p-block the lower oxidation states are favoured by the heavier members (due to inert pair effect), the opposite is true in the groups of J-block.For example, in group 6, Mo (VI) and W (VI) are found to be more stable than Cr (VI). Thus Cr (VI) in the form of dichromate in acidic medium is a strong oxidising agent, whereas MOO₃ and WO₃ are not.