`Cu^(2+)` is more stable than `Cu^+` in aqueous solution. Explain.

Explanation

`Cu^+` has outermost electronic configuration as `3d^(10)` and therefore, should be most common and most stable state because of extra stability associated with completely filled d-subshell `(d^10)`. However, this is not true and `Cu^(2+)` with outer electronic configuration `3d^9` is more stable than `Cu^+`. This is due to high hydration energy in aqueous solution and high lattice energy in solid state of `Cu^(2+)` as compared to `Cu^+`. The equilibrium :
`2 Cu^+ `K = ([Cu^(2+)])/([Cu^(+)]^(2)) = 1.6 xx 10^6`
The constant fordisproportionation of `Cu^+` in aqueous solution shows that `Cu^(2+)` is very stable in aqueous solution as compared to `Cu^+`.