Question

The correct order of ionic radii of $Y^{3+},L{a}^{3+},E{u}^{3+}$ and $L{u}^{3+}$ is (Atomic nos. $Y=39,La=57,Eu=63,Lu=71$ )

• A. $L{a}^{3+}<E{u}^{3+}<L{u}^{3+}<Y^{3+}$
• B. $Y^{3+}<L{a}^{3+}<E{u}^{3+}<L{u}^{3+}$
• C. $Y^{3+}<L{u}^{3+}<E{u}^{3+}<L{a}^{3+}$
• D. $L{u}^{3+}<E{u}^{3+}<L{a}^{3+}<Y^{3+}$

Answer 1

Answer: (C)

In lanthanide series there is a regular decrease in the atomic as well as ionic radii of trivalent ions $\left(M^{3+}\right)$ as the atomic number increases. Although the atomic radii do show some irregularities but ionic radii decreases from La $(103pm)$ to $Lu(86pm).Y^{3+}$ belong to second transition series therefore have greater ionic radii then other ions of third transition series.