Question

Compare the chemistry of the actinoids with that of lanthanoids with reference to: (i) electronic configuration (ii) oxidation states and (iii) chemical reactivity

Answer 1

(i) Electronic configuration
Lanthanoids have general electronic configuration $\left[Xe\right]4f^{1-14}5d^{0-1}6s^2$. Actinoids have general electronic configuration $\left[Rn\right]5f^{1-14}6d^{0-1}7s^2$ .
In lanthanoids, 4f orbital is filled and in actiniods, 5f orbital is filled.
(ii) Oxidation state
Apart from +3 oxidation state, lanthanoids show +2 and +4 oxidation states due to large energy gap between 4f and 5d subshells. Whereas actinoids show large number of oxidation states due to small energy gap between 5f and 6d subshells.
(iii) Chemical reactivity
Highly electropositive lanthanoids have almost similar chemical reactivity. Actinoids (electropostive and highly reactive) are more reactive (specially in finely divided state) than lanthanoids.