The chemistry of the actinoid elements is not so smooth as that of the lanthanoids. Justify this statement by giving some examples from the oxidation state of these elements.

Explanation

Lanthanoids show only few oxidation states viz., +2, +3 and + 4 (the most common oxidation state is +3). This is due to large energy gap between 4f - and 5d - subshells. The common oxidation state of a actinoids is also + 3, but they exhibit a large number of oxidation states, e.g., U, Np, Pu and Am exhibit oxidation states of + 3, +4, + 5 and + 6, in addition Np and Pu show oxidation states of + 7. This is due to small energy gap between 5f, 6d and 7s - orbitals. It is now easy to understand that due to large number of oxidation states, the chemistry of actinoid elements is not so smooth as that of the lanthanoids.