Question

The common stable oxidation states of Eu and Gd are respectively

• A. +3 and +3
• B. +3 and +2
• C. +2 and +3
• D. +2 and +2

Hint:

Lanthanide exceptions: \begin{itemize} \item Eu$^{2+}$ and Yb$^{2+}$ stable (half/full filled) \item Most lanthanides prefer +3 \end{itemize}

Answer 1

The Correct Option is C

Concept: Lanthanides generally show +3 oxidation state. Exceptions occur due to extra stability of: \begin{itemize} \item Half-filled or fully filled 4f orbitals \end{itemize} Step 1: Europium (Eu) Eu$^{2+}$ configuration: \[ [\text{Xe}] 4f^7 \] Half-filled 4f shell $\Rightarrow$ highly stable. Thus Eu commonly shows +2. Step 2: Gadolinium (Gd) Gd$^{3+}$ configuration: \[ [\text{Xe}] 4f^7 \] Half-filled stability occurs at +3 state. Thus Gd prefers +3. Conclusion: \[ \text{Eu}^{2+}, \quad \text{Gd}^{3+} \]