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Question: Answered & Verified by Expert
Arrange the following ions in the correct order with respect to their ionic radii.
ChemistryClassification of Elements and Periodicity in PropertiesTS EAMCETTS EAMCET 2020 (14 Sep Shift 2)
Options:
  • A $\mathrm{Br}^{-}>\mathrm{Cl}^{-}>\mathrm{Na}^{+}>\mathrm{Be}^{2+}$
  • B $\mathrm{Be}^{2+}>\mathrm{Na}^{+}>\mathrm{Cl}^{-}>\mathrm{Br}^{-}$
  • C $\mathrm{Cl}^{-}>\mathrm{Br}^{-}>\mathrm{Na}^{+}>\mathrm{Be}^{2+}$
  • D $\mathrm{Na}^{+}>\mathrm{Be}^{2+}>\mathrm{Br}^{-}>\mathrm{Cl}^{-}$
Solution:
1229 Upvotes Verified Answer
The correct answer is: $\mathrm{Br}^{-}>\mathrm{Cl}^{-}>\mathrm{Na}^{+}>\mathrm{Be}^{2+}$
The electronic configuration of $\mathrm{Be}^{2+}$ is $\left[{ }_2 \mathrm{He}\right], \mathrm{Na}^{+}$is $\left[{ }_{10} \mathrm{Ne}\right], \mathrm{Cl}^{-}$is $\left[{ }_{18} \mathrm{Ar}\right]$ and $\mathrm{Br}^{-}$ is $\left[{ }_{36} \mathrm{Kr}\right]$.
We know, site of group 18 elements follow the order $\mathrm{He} < \mathrm{Ne} < \mathrm{Ar} < \mathrm{Kr} < \mathrm{Xe}$.
So, the order of ionic radii of the given ions will be
$\mathrm{Br}^{-}>\mathrm{Cl}^{-}>\mathrm{Na}^{+}>\mathrm{Be}^{2+}$

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