The correct order of ionic radii for the ions,

Question:

The correct order of ionic radii for the ions, $\mathrm{P}^{3-}, \mathrm{S}^{2-}$, $\mathrm{Ca}^{2+}, \mathrm{K}^{+}, \mathrm{Cl}^{-}$is :

  1. $\mathrm{P}^{3-}>\mathrm{S}^{2-}>\mathrm{Cl}^{-}>\mathrm{K}^{+}>\mathrm{Ca}^{2+}$

  2. $\mathrm{Cl}^{-}>\mathrm{S}^{2-}>\mathrm{P}^{3-}>\mathrm{Ca}^{2+}>\mathrm{K}^{+}$

  3. $\mathrm{P}^{3-}>\mathrm{S}^{2-}>\mathrm{Cl}^{-}>\mathrm{Ca}^{2+}>\mathrm{K}^{+}$

  4. $\mathrm{K}^{+}>\mathrm{Ca}^{2+}>\mathrm{P}^{3-}>\mathrm{S}^{2-}>\mathrm{Cl}^{-}$


Correct Option: 1

Solution:

$\mathrm{P}^{3-}>\mathrm{S}^{2-}>\mathrm{Cl}^{-}>\mathrm{K}^{+}>\mathrm{Ca}^{2+}$

(Correct order of ionic radii)

all the given species are isoelectronic species. In isoelectronic species size increases with increase of negative charge and size decreases with increase in positive charge.

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