Account for the following: (i) `Cu^(+)` ions are not stable in aqueous solution.
(ii) Most of the transition metal ions exhibit paramagnetic behaviour.

Explanation

(i) `Cu^(+)` is unstable in aqueous solution due to lower hydration energy and higher reduction potential.
(ii) The transition elements involve the partial filling of d-subshells. Most of the transition metal ions have unpaired electrons in d-subshell (from `d^(1 to 10)` ) and therefore they give rise to paramagnetic character.