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.
Lanthanoids show limited number of oxidation states as +2, +3 and +4 (out of which +3 is most common). This is due to the large energy gap between 4 f and 5^-subshells. The dominant oxidation state of actinoids is also +3 but they show a number of other oxidation states also like uranium (Z = 92) and plutonium (Z = 94) show +3, +4, +5 and +6, neptunium (Z = 93) shows +3, +4+5 and +7. This is due to small energy difference between 5f, (6d and 7s-subshells of actinoids.