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

Lanthanoids show limited number of oxidation state, viz., + 2, + 3 and + 4 (out of which + 3 is most common). This is because of large energy gap between 4 f and 5 d subshells. The dominant oxidation state of actionoids is also + 3 but they show a number of other oxidation states also, e.g., uranium (Z = 92) and plutonium (Z = 94), show + 3, + 4, + 5 and + 7 etc. This is due to small energy difference between 5 f, 6 d and 7 s subshells of the actinoids.