Question

Which of the following will have a spin-only magnetic moment of 2.86 BM?

• A. \(\text{[CoF}_6]^{3-}\)
• B. \(\text{[Co(NH}_3)_6]^{3+}\)
• C. \(\text{[NiCl}_4]^{2-}\)
• D. \(\text{[Ni(CN)}_4]^{2-}\)

Hint:

A magnetic moment of 2.86 BM corresponds to 2 unpaired electrons, which is typical for \(d^8\) transition metal ions like Ni\(^{2+}\).

Answer 1

The Correct Option is C

Step 1: Determine the Magnetic Moment - The magnetic moment (\(\mu\)) for a transition metal complex can be calculated using the formula: \[ \mu = \sqrt{n(n+2)} \, \text{BM}, \] where \(n\) is the number of unpaired electrons. 

 

Step 2: Analyze the Complexes - \(\text{[NiCl}_4]^{2-}\): Nickel in the +2 oxidation state (\(d^8\)) has 2 unpaired electrons, which gives a spin-only magnetic moment of 2.86 BM. Hence, the correct answer is \(\text{[NiCl}_4]^{2-}\).