Periodic Classification and Periodic Properties 2 Question 27
27. Ionic radii of
(a) $\mathrm{Ti}^{4+}<\mathrm{Mn}^{7+}$
(b) ${ }^{35} \mathrm{Cl}^{-}<{ }^{37} \mathrm{Cl}^{-}$
(c) $\mathrm{K}^{+}>\mathrm{Cl}^{-}$
(d) $\mathrm{P}^{3+}>\mathrm{P}^{5+}$
(1999, 3M)
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Answer:
Correct Answer: 27. (d)
Solution:
- (a) $\mathrm{Ti}^{4+}>\mathrm{Mn}^{7+}$ is the correct order of size due to lower positive charge on $\mathrm{Ti}^{4+}$.
(b) ${ }^{37} \mathrm{Cl}^{-}={ }^{37} \mathrm{Cl}^{-}$: Isotopes with same charge have same size because isotopes differ in compositions of nuclei which do not affect the atomic/ionic radius.
(c) $\mathrm{K}^{+}<\mathrm{Cl}^{-}$is the correct order. Among isoelectronic species, anion has greater size than cation.
(d) $\mathrm{P}^{3+}>\mathrm{P}^{5+}$ is the correct order. For the same elements, lower the positive charge, larger the ions.
