Answer:-

Cerium (Ce) and terbium (Tb) are two elements that can exhibit a +4 oxidation state and behave as good oxidizing agents. This behavior is primarily due to their electronic configurations and the relative stability of the +4 oxidation state for these elements.

Let’s look at each element individually:

1. Cerium (Ce):

   • Cerium is a lanthanide element with the atomic number 58. In its ground state, cerium has the electronic configuration [Xe] 4f¹ 5d¹ 6s². When cerium undergoes oxidation to achieve a +4 oxidation state, its electron configuration becomes [Xe] 4f⁰ 5d⁰ 6s².
   • The transition from the 4f¹ electron configuration to 4f⁰ involves the removal of one electron from the 4f orbital, which leaves an empty 4f orbital.
   • An empty or partially filled f orbital can make the +4 oxidation state more stable for cerium because it minimizes electron-electron repulsions in the 4f orbitals. This stability encourages cerium to accept electrons from other species, making it a good oxidizing agent in the +4 oxidation state.

2. Terbium (Tb):

   • Terbium is another lanthanide element with the atomic number 65. In its ground state, terbium has the electronic configuration [Xe] 4f⁹ 6s². When terbium undergoes oxidation to achieve a +4 oxidation state, its electron configuration becomes [Xe] 4f⁷ 6s².
   • The transition from the 4f⁹ electron configuration to 4f⁷ involves the removal of two electrons from the 4f orbitals, resulting in a partially filled 4f subshell.
   • The presence of partially filled 4f orbitals in the +4 oxidation state makes terbium relatively stable in this state, making it a good oxidizing agent.

In both cases, the stability of the +4 oxidation state is associated with the electronic configurations that result in either empty or partially filled f orbitals. These configurations minimize electron-electron repulsions, making it energetically favorable for cerium and terbium to exist in the +4 oxidation state. As a result, they are capable of accepting electrons from other substances, acting as good oxidizing agents when they are in the +4 oxidation state.