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

Assign reason for the following: Copper (I) ion is not known in aqueous solutions.
`2Cu^(+) rarr Cu^(2+) + 2 Cu`
The greater stability of `Cu^(2+)` ion as compared to `Cu^+` is due to the much more negative `Delta_(hydH)` of `Cu^(2+)` than `Cu_((aq))^(+)` which mor than compensates for the second ionization enthalpy of Cu.