With the help of crystal field theory, predict the number of unpaired electrons in `[Fe(CN)_6]^(4-)`

Explanation

To determine the number of unpaired electrons in the complex ion \([Fe(CN)_6]^{4-}\) using crystal field theory, we can follow these steps:

### Step 1: Determine the oxidation state of iron (Fe)
The overall charge of the complex is \(-4\). The cyanide ion (\(CN^-\)) has a charge of \(-1\). Since there are 6 cyanide ions, the total negative charge contributed by the cyanide ions is \(-6\).

Let the oxidation state of iron be \(x\). The equation for the overall charge is:
\[
x + 6(-1) = -4
...