Question

Which one of the following groupings represents a collection of isoelectronic species? (At. nos.: Cs-55, Br-35)

(a) Na⁺ , Ca²⁺ , Mg²⁺ 

(b) N^3– , F^– , Na⁺

(c) Be, Al³⁺ , Cl^– 

(d) Ca²⁺ , Cs⁺ , Br.

Answer 1

(b) : Isoelectronic species are the neutral atoms, cations or anions of different elements which have the same number of electrons but different nuclear charge. 

Number of electrons in N^3– = 7 + 3 = 10. 

Number of electrons in F^– = 9 + 1 = 10 

Number of electrons in Na⁺ = 11 – 1 = 10.