Which of the following forms stable +4 oxidation state ?

Options

A. La
B. Gd
C. Eu
D. Ce

Answer

D

Explanation

We know that, according to Hund's rule atoms or ions having empty, half filled and completely filledorbitals are most stable. `C^(4+)` ion has configuration `6s^(0), 4f^(0), 5d^(0).` Hence `+4` oxidation state of cerium is most stable due to `4f^(0)` configureation, and it act as oxidising agent.