The stability of Cu ^ 2 + is more than Cu ^ + salts in aqueous...

The stability of ${Cu}^{2 +} ( aq )$ rather than ${Cu}^{+} ( aq )$ is due to the much more negative ${∆}_{hyd}{H}^{o}$ of ${Cu}^{2 +} ( aq )$ than ${Cu}^{+}$, which more than compensates for the second ionisation enthalpy of $Cu$. The ${Cu}^{2 +}$ ion has a greater charge density than ${Cu}^{+}$ ion and thus forms much stronger bonds releasing more hydration energy.