Question

The correct order of ionic radii of $Ce,La,Pm$ and $Yb$ in its $+3$ oxidation state is:

• A. $L{a}^{3+}<P{m}^{3+}<C{e}^{3+}<Y{b}^{3+}$
• B. $L{a}^{3+}<C{e}^{3+}<P{m}^{3+}<Y{b}^{3+}$
• C. $Y{b}^{3+}<C{e}^{3+}<P{m}^{3+}<L{a}^{3+}$
• D. $Y{b}^{3+}<P{m}^{3+}<C{e}^{3+}<L{a}^{3+}$

Answer 1

The correct option is D $Y{b}^{3+}<P{m}^{3+}<C{e}^{3+}<L{a}^{3+}$

Due to lanthanoid contraction, the ionic radii decreases in f-block elements from $La$ to $Lu$.
Hence the correct order of ionic radius is: $Y{b}^{3+}<P{m}^{3+}<C{e}^{3+}<L{a}^{3+}$