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

Explanation

To understand why europium (II) is more stable than cerium (II), we need to analyze their electronic configurations and the stability associated with half-filled subshells.

### Step-by-Step Solution:

1. **Identify the Electronic Configurations:**
- Europium (Eu) has an atomic number of 63. Its electronic configuration in the +2 oxidation state (Eu²⁺) is:
\[
\text{Eu}^{2+}: [Xe] 4f^7 5d^0
...