Question

The correct increasing order of ionic radii of the following $C{e}^{3+}$,
$L{a}^{3+},P{m}^{3+}\text{and}Y{b}^{3+}$ is

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

Answer 1

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

The ionic radii of the lanthanides decrease from 103 pm $\left(L{a}^{3+}\right)$ to 86 pm ($L{u}^{3+})$ in the lanthanide series. Across the lanthanide series, electrons are added to the 4f shell.
Because of concentration of lanthanide, the size of $+3$ ions decreases from $L{a}^{3+}$ to $L{u}^{3+}$.
Option (a) is correct