Which of the following statement is correct?

To determine the correct statement, let us analyze the chemistry of Cerium (Ce):

1. Electronic Configuration of Cerium (Ce):
Cerium is the first element of the lanthanide series with atomic number 58. Its ground-state electronic configuration is:
Ce = [Xe] 4f¹ 5d¹ 6s²

2. Oxidation States and Configurations:
When Cerium loses four electrons, it forms the Ce⁴⁺ ion. The electronic configuration of Ce⁴⁺ is:
Ce⁴⁺ = [Xe]
This gives Ce⁴⁺ a stable noble gas configuration. However, the Ce³⁺ ion has the configuration [Xe] 4f¹, meaning it does not possess a noble gas configuration.

3. Stability and Oxidizing Behavior:
In aqueous solutions, the +3 oxidation state (+3) is the most stable and dominant oxidation state for lanthanides due to hydration and ionization energies. Although Ce⁴⁺ has a noble gas core, it is thermodynamically less stable than Ce³⁺ in solution. Thus, Ce⁴⁺ has a strong tendency to gain an electron and get reduced to Ce³⁺ according to the following reaction:

${\mathrm{Ce}}^{4+}+e^{-}\to {\mathrm{Ce}}^{3+}$

Since Ce⁴⁺ readily gains an electron (undergoes reduction), it acts as a strong oxidizing agent.