Question

The correct order of ionic radii of Y³⁺, La³⁺, Eu³⁺
and Lu³⁺ is
(a) La ³⁺ < Eu³⁺ < Lu ³⁺ < Y³⁺
(b) Y³⁺ < La ³⁺ < Eu³⁺ < Lu³⁺
(c) Y³⁺ < Lu ³⁺ < Eu³⁺ < La ³⁺
(d) Lu³⁺ < Eu³⁺ < La³⁺ < Y³⁺
(Atomic nos. Y =39, La = 57, Eu = 63, Lu = 71)

Answer 1

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(d)

Answer 2

(c) Y³⁺ < Lu ³⁺ < Eu³⁺ < La ³⁺

Explanation:

The correct order is Y³⁺ < Lu ³⁺ < Eu³⁺ < La ³⁺. The Y³⁺ ion has the least atomic number and hence the lease ionic radii as well. Eu and Lu are members of lanthanoid series and La is a rare earth element that lie above Eu and Lu in the periodic table. The ionic radii decreases as we move down the group. So La has a bigger ionic radii than Lu and Eu.

Y³⁺ < Lu ³⁺ < Eu³⁺ < La ³⁺

Option C is the answer.