Regarding the coloration and magnetic properties of aqueous lanthanoid ions (), which of the followi — d and f Block Elements Chemistry Question

💡 Solution & Explanation

$La^{3+}$ ($4f^0$) and $Lu^{3+}$ ($4f^{14}$) have no unpaired f-electrons to undergo transitions, making them colourless and diamagnetic. The colour in other ions arises from $f-f$ transitions. Because they contain unpaired electrons, all other $Ln^{3+}$ ions are paramagnetic, not diamagnetic. $Gd^{3+}$ ($4f^7$) has exactly $7$ unpaired electrons, the absolute maximum.