The ionization energies of copper and silver are

First ionization energy: Cu-745.5 kJ/mol Ag-731.0 kJ/mol

Second ionization energy: Cu-1958 kJ/mol Ag-2073 kJ/mol

Now, looking at the ionization energies, it is quite clear why $\ce{Cu^2+}$ is formed readily but only $\ce{Ag+}$ is usually observed.

The first ionization energies can be rationalized by the fact that Ag is larger in size than Cu.

However, the second ionization energy of Cu should be higher than second ionization energy of Ag because in case of Cu the electron is being taken from the 3d orbital while it is being taken from 4d orbital in case of Ag. 4d orbital should be larger than 3d orbitals and so, the energy required to pull electron from 4d orbital should be lower than that in case of 3d orbital.

Is there any explanation to this anomaly?


But 4d electrons are attracted more than 3d electrons. Ag along with 4d also has 3d electrons which have weaker shielding effect. So nuclear charge attracts 4d electrons more than 3d. It is just like lanthanoid contraction.


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