The D And F Block Elements Ques 77
77. The correct order of ionic radii of $Y^{3+}, La^{3+}, Eu^{3+}$ and $Lu^{3+}$ is
[2003]
(a) $La^{3+}<Eu^{3+}<Lu^{3+}<Y^{3+}$
(b) $Y^{3+}<La^{3+}<Eu^{3+}<Lu^{3+}$
(c) $La^{3+}<Eu^{3+}<Lu^{3+}<Y^{3+}$
(d) $Y^{3+}<Lu^{3+}<Eu^{3+}<La^{3+}$
(Atomic nos. $Y=39, La=57, Eu=63, Lu=71$ )
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Solution:
- (c) In lanthanide series there is a regular decrease in the atomic as well as ionic radii of trivalent ions $(M^{3+})$ as the atomic number increases. Although the atomic radii do show some irregularities, the ionic radii decreases from $La(103 pm)$ to $Lu(86 pm)$.
BETA
