GC Atomic Structure

Which of the following pairs represents isoelectronic ions

  1. Mg2+, Ca2+
  2. Na+, K+
  3. K+, Mg2+
  4. Ca2+, S2-


Isoelectronic ions has same number of electrons.

Atomic number of Ca is 20. Ca2+ has 18 electrons. Atomic number of S is 16. S2- has 18 electrons.

The correct option is D.