The value of magnetic moment for \([CoF_6]^{3-}\) is:

4.9 BM

The correct answer is option 4. 4.9 BM.

The given complex is \([CoF_6]^{3+}\).

Here, the central metal \(Co\) is in \(+3\) oxidation state. Thus the electronic configuration will be:

\(Co^{3+} = [_{18}Ar] 3d^4 4s^0\)

Thus the number of unpaired electrons, \(n = 4\)

We know,

\(\mu = \sqrt{n(n + 2)} BM\)

or, \(\mu = \sqrt{4(4 + 2)}BM\)

or, \(\mu = \sqrt{24}BM\)

or, \(\mu = 4.9 BM\)