The Actinoids

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 configuration: Half-filled 4f shell highly stable. Thus Eu commonly shows +2. Step 2: Gadolinium (Gd) Gd configuration: Half-filled stability occurs at +3 state. Thus Gd prefers +3. Conclusion: