In which of the following pairs, the ions are iso-electronic?

(i) Na⁺, Mg²⁺

(ii) Al³⁺, O^–

(iii) Na⁺, O^2-

(iv) N^3-, Cl^–

Correct Answers: (i) Na⁺, Mg²⁺  (iii) Na⁺, O^2-

Explanation: Isoelectronic species are the atoms / ions that has the same number of electrons.