Which of the following lanthanoid ions is completely colourless and diamagnetic because it lacks unp — d and f Block Elements Chemistry Question

💡 Solution & Explanation

Lutetium ($Lu^{3+}$) has a completely filled $4f^{14}$ subshell. With zero unpaired electrons, it cannot undergo $f-f$ transitions (making it colourless) and is entirely diamagnetic. $La^{3+}$ ($4f^0$) also shares these properties.