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NEETChemistryd and f Block Elements

The calculated 'spin-only' magnetic moment of Co ²⁺ ion is :

Options

  1. A3.87 BM
  2. B5.92 BM
  3. C7.93 BM
  4. D2.84 BM

Correct answer

A. 3.87 BM

Step-by-step solution

The atomic number of Co is 27 . The electronic configuration of a neutral Co atom is [ Ar ] 3d^7 4s^2 . When forming the Co ²⁺ ion, two electrons are removed from the outermost 4s orbital, giving the configuration [ Ar ] 3d^7 . According to Hund's rule, filling the five degenerate d -orbitals with 7 electrons results in 3 unpaired electrons ( n = 3 ). The spin-only magnetic moment is calculated using the formula = n(n+2) BM . Substituting n = 3 : = 3(3+2) = 15 3.87 BM . Answer: 3.87 BM

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