Chemistry - f-block Question with Solution | TestHub

Due to Lanthanoid contraction their is greater decrease in ionic radii of elements in lanthanide series because of poor shielding of nuclear charge by$4\mathrm{f}$electrons, hence the order will be$\mathrm{Y}{\mathrm{b}}^{+3}<\mathrm{P}{\mathrm{m}}^{3+}<\mathrm{C}{\mathrm{e}}^{+3}<\mathrm{L}{\mathrm{a}}^{3+}$