MDCAT Chemistry MCQ #916

Which pair of species has the same number of electrons but different atomic numbers?

MDCAT Chemistry MCQ #916

  1. Question 1

    Q1. Which pair of species has the same number of electrons but different atomic numbers?

    • A) Cl⁻ and Ar
    • B) Na⁺ and Ne
    • C) O²⁻ and F⁻
    • D) Mg²+ and Al³+

    Answer: Cl⁻ and Ar

    Explanation: Cl⁻ (18 electrons) and Ar (18 electrons) are isoelectronic. Other pairs differ in charge or atomic numbers.