How many unpaired electrons are present in the high spin form of [CoF₆]^3- complex and which metal orbitals are used in bonding?

4 unpaired electrons and 4s, 4p and 4d orbitals to give sp³d² hybridisation.

The correct answer is option 3. 4 unpaired electrons and 4s, 4p and 4d orbitals to give sp³d² hybridisation.

The atomic number of the central metal ion, \(Co\) is 27.

The electronic configuration of the central metal ion is

\(_{27}Co = [_{18}Ar] 4s^2 3d^7\)

Let the oxidation of the central metal ion be \(x\). Then

\(x + 6(-1) = -3\)

or, \(x - 6 = -3\)

or, \(x = +3\)