CDS 2026 (I) General Knowledge, question 24

Topic: Chemistry

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Q24

Which one among the following pairs is not correctly matched ?

  1. (a) Nitrogen : Three unpaired electrons
  2. (b) Carbon : Tetravalent
  3. (c) Chlorine : Two stable isotopic forms
  4. (d) Helium : Diatomic gasCorrect answer

Solution.

Answer: (d) Helium : Diatomic gas

  1. Helium is monatomic under ordinary conditions, not diatomic.
  2. Ground-state nitrogen has three unpaired 2p electrons, carbon commonly shows valency four, and naturally occurring chlorine has two stable isotopes, chlorine-35 and chlorine-37.