Why is europium (II) more stable than cerium (II) ?

Explanation

Europium (II) has electronic configuration `[Xe] 4f^(7) 5d^0` while cerium (II) has electronic configuration `[Xe] 4f^1 5d^1`, In` Eu^(2+),` 4f subshell is half filled and 5d-subshell is empty. Since half filled and completely filled electronic configurations are more stable, `Eu^(2+)` ion is more stable than `Ce^(2+)` in which neither 4 subshell nor 5d subshell is half filled or completely filled