Some lanthanoid elements exhibit stable oxidation states other than to achieve empty, half-filled, o — d and f Block Elements Chemistry Question

💡 Solution & Explanation

The universally stable state for all lanthanoids is $+3$. $Eu^{2+}$ ($4f^7$) and $Sm^{2+}$ ($4f^6$) have a strong thermodynamic tendency to lose one electron to reach the $+3$ state, thus acting as strong reducing agents. $Ce^{4+}$ ($4f^0$) has a strong tendency to gain an electron to reach $+3$, acting as a powerful oxidizing agent. $Yb^{2+}$ ($4f^{14}$) also tends to lose an electron to become $+3$, making it a reducing agent, not an oxidizing agent.