Home › MCQs › NEET Chemistry › Question #7405
Back to Questions
NEET Chemistry QUESTION #7405
Question 1
The correct decreasing order of ionic radii among the following isoelectronic species is:
  • \(\text{K}^+ > \text{Ca}^{2+} > \text{Cl}^- > \text{S}^{2-}\)
  • \(\text{Ca}^{2+} > \text{K}^+ > \text{S}^{2-} > \text{Cl}^-\)
  • \(\text{Cl}^- > \text{S}^{2-} > \text{Ca}^{2+} > \text{K}^+\)
  • \(\text{S}^{2-} > \text{Cl}^- > \text{K}^+ > \text{Ca}^{2+}\)✔️
Correct Answer Explanation
All are isoelectronic (18 electrons). Decreasing size = increasing nuclear charge:
  • \(\text{S}^{2-}\): Z=16 → largest
  • \(\text{Cl}^-\): Z=17
  • \(\text{K}^+\): Z=19
  • \(\text{Ca}^{2+}\): Z=20 → smallest
Decreasing order: \(\text{S}^{2-} > \text{Cl}^- > \text{K}^+ > \text{Ca}^{2+}\)