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NEET CHEMISTRYEasy

Which one of the following represents all isoelectronic species?

A

Na⁺, Cl⁻, O⁻, NO⁺

B

N₂O, N₂O₄, NO⁺, NO

C

Na⁺, Mg²⁺, O⁻, F⁻

D

Ca²⁺, Ar, K⁺, Cl⁻

Step-by-Step Solution

Isoelectronic species are atoms or ions that contain the same number of electrons (NCERT Section 3.7.1). We calculate the total number of electrons for the species in the correct option:

  1. Ca²⁺: Atomic number (Z) of Calcium is 20. It loses 2 electrons. Total electrons = 20 - 2 = 18.
  2. Ar: Argon is a noble gas with atomic number 18. Total electrons = 18.
  3. K⁺: Atomic number of Potassium is 19. It loses 1 electron. Total electrons = 19 - 1 = 18.
  4. Cl⁻: Atomic number of Chlorine is 17. It gains 1 electron. Total electrons = 17 + 1 = 18.

Since all species possess 18 electrons, they are isoelectronic. (Note: In Option 3, Na⁺, Mg²⁺, and F⁻ have 10 electrons, but O⁻ has 9 electrons; O²⁻ would have been isoelectronic).

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