Question

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

Answer 1

Eu (Z = 63)

Electronic configuration – [Xe] 4f⁷ 5d⁰ 6s²

Eu²⁺ – Electronic configuration Electronic 6s¹

Ce (Z = 58)

Electronic configuration – [Xe] 4f²⁺ 5d⁰ 6s²⁺

Ce²⁺ – Electronic confluration – [Xe] 4f² 5d⁰

According to the Aufbau principle, half-filled and completely filled d (or) f orbitals are more stable than partially filled f orbitals.

Hence Eu²⁺ [Xe] 4f⁷ 5d⁰ is more stable than Ce²⁺ [Xe] 4f² 5d⁰