Question

Which one of the following sets of ions represents a collection of isoelectronic species?
(a) K⁺ , Cl^– , Ca²⁺ , Sc³⁺
(b) Ba²⁺ , Sr²⁺ , K⁺ , S^2–
(c) N^3– , O^2– , F^– , S^2–
(d) Li⁺ , Na⁺ , Mg²⁺ , Ca²⁺ .

Answer 1

(a) : K⁺ = 19 – 1 = 18e^–
Cl^– = 17 + 1 = 18e^–
Ca²⁺ = 20 – 2 = 18e^–
Sc³⁺ = 21 – 3 = 18e^–
Thus all the species are isoelectronic.