Question:medium

The correct order of decreasing ionic radii among the following isoelectronic species
  1. \(K^+, \, Ca^{2+}, \, Cl^-, \, S^{2-}\)
  2. \(K^+, \, Cl^-, \, Ca^{2+}, \, S^{2-}\)
  3. \(S^{2-}, \, Ca^{2+}, \, Cl^-, \, K^+\)
  4. \(S^{2-}, \, Cl^-, \, K^+, \, Ca^{2+}\)
Choose the correct answer from the options given below:

Show Hint

In isoelectronic species, ionic radii are inversely proportional to the effective nuclear charge (Zeff).
Updated On: Feb 10, 2026
  • (A) > (B) > (C) > (D)
  • (A) > (C) > (B) > (D)
  • (D) > (B) > (C) > (A)
  • (D) > (C) > (A) > (B)
Show Solution

The Correct Option is D

Solution and Explanation

In an isoelectronic series, a greater nuclear charge results in a smaller ionic radius. Consequently, the ionic radii of the given isoelectronic species decrease in the following order, corresponding to increasing nuclear charge: \[ \text{S}^{2-} > \text{Cl}^- > \text{K}^+ > \text{Ca}^{2+}. \] \( \text{S}^{2-} \) possesses the smallest nuclear charge, while \( \text{Ca}^{2+} \) has the largest.
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