Question

Account for the following:
$C{{u}^{+}}$is unstable in an aqueous solution.

Answer 1

The bigger is the size of the atom and the more the electrons are far from the nucleus, the more polarizable it will be. If the atom is more polarizable then more steady will be the anion. If the particle is more electronegative than more steady will be the anion. The ion is said to be more stable if it has a fully filled or half filled orbital.

Complete step-by-step answer: To know whether the orbital of atom or ion is fully filled or half filled we should know the electronic configuration of the substance. The electronic configuration helps us in describing how the electrons are distributed in the atomic orbitals.
The atomic number of Cu is 29. So the electronic configuration of copper is $[Ar]3{{d}^{10}}4{{s}^{1}}$. As in $C{{u}^{+}}$one electron is removed so the electronic configuration will be $[Ar]3{{d}^{10}}$. Though the $C{{u}^{+}}$ion has a fully filled d orbital but still it is not stable in aqueous solution. In the aqueous solution the $C{{u}^{2+}}$ion is more stable than $C{{u}^{+}}$ion. this is so because although the energy is required to remove one electron from the $C{{u}^{+}}$to form $C{{u}^{2+}}$ion but the high hydration energy of the $C{{u}^{2+}}$compensates for it. So the $C{{u}^{+}}$ion is unstable in aqueous medium and undergoes the disproportional reaction and give $C{{u}^{2+}}$and Cu as the products. It gets oxidised to give cuprous ion and reduced to give copper metal.

Note: In the aqueous medium the particles of water legitimately are connected to the particles of metal are said to have the place with the main coordination circle known as the solvation shell. The other name of the solvation shell is first shell or essential shell. The connection present between the metl particle and the water atom is known as the dative covalent bond.