Which of the following lanthanoid ions is completely diamagnetic in nature due to the total absence — d and f Block Elements Chemistry Question

💡 Solution & Explanation

To be completely diamagnetic, an ion must have zero unpaired electrons (an empty $f^0$ or fully filled $f^{14}$ subshell). $Yb$ ($Z=70$) has the ground state configuration $[Xe] 4f^{14} 6s^2$. When it loses two electrons to form $Yb^{2+}$, it achieves the configuration $[Xe] 4f^{14}$, leaving no unpaired electrons. Thus, it is purely diamagnetic. $Eu^{2+}$ is $4f^7$ (paramagnetic).