Assign reasons for the following :
(i) Copper (I) ion is not known in aqueous solution.
(ii) Actinoids exhibit greater range of oxidation states than lanthanoids.

Explanation

(i) See Q. 29 (iii), Set-I, Outside Delhi., 2010,
(ii) In actionoids energy gap between Sf, 6d and 7S is very small hence all e-s participate in bonding whereas in lanthanolds, energy gap between 4£ and 5d is very large hence all e- s cannot participate so that less no. of oxidation states.