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MHT CET202525 Apr 2025Morning ShiftChemistryCoordination CompoundsActual

What is the number of unpaired electrons in [ Co ( NH ₃ )₆ ]³⁺ complex?

Options

  1. A4
  2. B3
  3. C2
  4. DZero

Correct answer

D. Zero

Step-by-step solution

The cobalt ion in [ Co ( NH ₃ )₆ ]³⁺ has an oxidation state of +3, giving it the configuration [ Ar ] 3d^6 . Ammonia is a strong field ligand that causes significant crystal field splitting in octahedral complexes. This favors electron pairing in the lower energy t_ 2g orbitals before occupying e_g orbitals. All six electrons pair completely in the three t_ 2g orbitals: There are zero unpaired electrons.

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