Question

Arrange $C{e}^{3+},L{a}^{3+},P{m}^{3+}$ and $Y{b}^{3+}$ in increasing order of their ionic radii.

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

Answer 1

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

According to their positions in the periods, these values are in the order.
$$\begin{array}{ccccc}& Y{b}^{3+}<& P{m}^{3+}<& C{e}^{3+}<& L{a}^{3+}\\ \text{At. Numbers}& 70& 61& 58& 57\\ \text{Ionic radii (pm)}& 86& 98& 103& 106\end{array}$$
This is due to lanthanide contraction.