Q. The correct order of the decreasing ionic radii among the following isoelectronic species is
A) K⁺ > Ca²⁺ > Cl⁻ > S²⁻
B) Ca²⁺ > K⁺ > S²⁻ > Cl⁻
C) Cl⁻ > S²⁻ > Ca²⁺ > K⁺
D) S²⁻ > Cl⁻ > K⁺ > Ca²⁺
Explanation
[Solution from source] All four ions have 18 electrons. Size falls as nuclear charge rises: S²⁻ (Z = 16) > Cl⁻ (17) > K⁺ (19) > Ca²⁺ (20). The orders putting cations first reverse this trend. Answer (4).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.