Question

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

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

Answer 1

Answer: (B)

The overall decrease in atomic and ionic radii from $L{a}^{3+}$ to $L{u}^{3+}$ is called lanthanoid contraction. Hence, the correct order is $Y{b}^{3+}<P{m}^{3+}<C{e}^{3+}<L{a}^{3+}$