Answer:-

Europium (Eu) and ytterbium (Yb) are two elements that can exhibit a +2 oxidation state and behave as good reducing agents. This behavior is primarily due to their electronic configurations and the relative stability of the +2 oxidation state for these elements.

Let’s examine each element individually:

1. Europium (Eu):

   • Europium is a lanthanide element with the atomic number 63. In its ground state, europium has the electronic configuration [Xe] 4f⁷ 6s². When europium undergoes oxidation to achieve a +2 oxidation state, its electron configuration becomes [Xe] 4f⁷ 6s⁰.
   • The transition from the 6s² electron configuration to 6s⁰ involves the removal of two electrons from the 6s orbital, leaving it empty.
   • An empty 6s orbital can make the +2 oxidation state more stable for europium because it minimizes electron-electron repulsions in the 6s orbital. This stability encourages europium to donate electrons to other species, making it a good reducing agent in the +2 oxidation state.

2. Ytterbium (Yb):

   • Ytterbium is another lanthanide element with the atomic number 70. In its ground state, ytterbium has the electronic configuration [Xe] 4f¹⁴ 6s². When ytterbium undergoes oxidation to achieve a +2 oxidation state, its electron configuration becomes [Xe] 4f¹⁴ 6s⁰.
   • The transition from the 6s² electron configuration to 6s⁰ involves the removal of two electrons from the 6s orbital, resulting in an empty 6s orbital.
   • An empty 6s orbital contributes to the stability of the +2 oxidation state for ytterbium by minimizing electron-electron repulsions in the 6s orbital. This stability promotes the donation of electrons by ytterbium, making it a good reducing agent in the +2 oxidation state.

In both cases, the stability of the +2 oxidation state is associated with the electronic configurations that result in empty 6s orbitals. These configurations minimize electron-electron repulsions, making it energetically favorable for europium and ytterbium to exist in the +2 oxidation state. As a result, they are capable of donating electrons to other substances, acting as good reducing agents when they are in the +2 oxidation state.