JEE Advanced 2025 · Paper 1, Chemistry question 6

An ion is diamagnetic when it has no unpaired electrons.

Ion	Configuration	Magnetism
$\ce{La^3+}$, $\ce{Ce^4+}$	[Xe] ($4f^0$)	diamagnetic
$\ce{Yb^2+}$, $\ce{Lu^3+}$	$4f^{14}$	diamagnetic
$\ce{La^2+}$	$5d^1$	paramagnetic
$\ce{Ce^3+}$	$4f^1$	paramagnetic
$\ce{Yb^3+}$	$4f^{13}$	paramagnetic
$\ce{Lu^2+}$	$5d^1$	paramagnetic

Both ions are diamagnetic only in pairs (A) and (B).