Question

The correct order of ionic radii of $Y ^{3+}, La ^{3+}$ $Eu ^{3+}$, and $Lu ^{3+}$ is : - Atomic nos. $Y =39,\, La =57,\, Eu =63,\, Lu =71$.

• A. $Lu^{3+ } < Eu^{3+} < La^{3+} < Y^{3+}$
• B. $La^{3+ } < Eu^{3+} < Lu^{3+} < Y^{3+}$
• C. $Y^{3+ } < La^{3+} < Eu^{3+} < Lu^{3+}$
• D. $Y^{3+ } < Lu^{3+} < Eu^{3+} < La^{3+}$

Answer 1

Answer: (D)

$Y^{3+ } < Lu^{3+} < Eu^{3+} < La^{3+}$

Answer 2

The correct order of ionic radii of $Y^{3+},La^{3+},Eu^{3+}$ and $Lu^{3+},$ is
$Y^{3+} < Lu^{3+} < Eu^{3+} < La^{3+}$ because Eu and Lu are the members of lanthanide series (so they show lanthanide contraction) and La is the representative element of all elements of such series and $Y^{3+}$ ion has lowei radii as comparison to $La^{3+}$ because it lies immediately above it in the periodic table.