GKFix MCQ Question

What is the primary electronic factor that differentiates the stability of Eu²⁺ from Eu³⁺?

• A. Eu²⁺ achieves a half-filled (4f⁷) configuration, while Eu³⁺ has a 4f⁶ configuration
• B. Eu²⁺ has a filled f-subshell, while Eu³⁺ has a half-filled f-subshell
• C. Eu²⁺ has no unpaired electrons, while Eu³⁺ has seven
• D. Eu²⁺ is diamagnetic, while Eu³⁺ is paramagnetic