Give reason for the following :
(i) Mn shows the highest oxidation state of +7 with oxygen but with fluorine, it shows the highest oxidation state of +4
(ii) Transition metals show variable oxidation states.
(iii) Actinoids show irregularities in their electronic configurations.

Explanation

(i) Manganese (Mn) shows highest oxidation state of +7 with oxygen but which fluorine, it shows the highest of +4 because has the ability to form multiple bonds with Manganese. Hence, oxidation state can be extended to +7.
(ii) Transition metals show variable oxidation state due to incomplete filling of d-orbitals. Moreover, their valence electrons are in `(n-1)^(4)` and ns orbitals whose energy difference is very less and both the energy orbitals can take part in bond formation.
(iii) In actinoids, 5f and 6d subshells are close in energy. The outer most 7S orbital remains filled. Electrons can easily jump from 5f to 6d or vice-versa. Irregularities in electronic configuration are also related to stabilities of `f^(@), f^(7)` and `f^(14)` occupancy of 5f orbitals. Moreover, they are radioactive with short lives.