Question

“Second ionization enthalpy of copper is very high”. Why?

Answer 1

Ionization energy can be elaborated as the energy required to remove an electron from the outermost shell of the orbital of an atom. A full filled orbital takes more ionization enthalpy than the other orbitals. One can analyze the electrons present in the orbitals of the copper element and decide the reason for the question.

Complete step by step answer:

1. First of all we will understand the concept of the ionization enthalpy of elements. The ionization means the removal of electrons and ionization enthalpy is the energy needed to remove an electron from an element's orbit.
2. Now let us analyze the copper element and its electronic configuration. The element copper has an atomic number as ${\text{29}}$ which means it has ${\text{29}}$ electrons revolving in its orbitals. Therefore, the electronic configuration of copper is as below,
   $Cu = 1{s^2},2{s^2},2{p^6},3{s^2},3{p^6},3{d^{10}},4{s^1}$
3. Now as we see there is only one electron in the outermost orbital of the copper that is in ${\text{4s}}$ orbital. As there is only one electron in the s-orbital it is easier to remove that electron because after losing the electron the copper can get a stabilized structure. Hence, to remove the first electron from copper there is less energy required which means the first ionization energy of copper is low.
4. Now when we try to remove the second electron which is from the d-orbital i.e. $3{d^{10}}$, there will be a need for high energy as this orbital is a fully filled orbital and fully filled orbitals are the most stable orbitals. Hence, to remove the electron from 3d-orbital there is a need for more energy as it disturbs the stability of the element. Therefore, the second ionization enthalpy of copper is very high.

Note:
The fully filled and the half-filled orbitals are the most stable orbitals and they have the highest ionization enthalpy. The lower is the principal quantum number of an element the higher will be the ionization energy of that element as the lower principal quantum number orbitals are close to the nucleus and there is the higher attraction of the electrons and protons which requires more energy to remove an electron.