With the help of crystal field theory, predict the number of unpaired electrons in `[Fe(H_2O)_6]^(2+)`

Explanation

To determine the number of unpaired electrons in the complex ion \([Fe(H_2O)_6]^{2+}\) using crystal field theory, we can follow these steps:

### Step 1: Determine the oxidation state of iron
The complex \([Fe(H_2O)_6]^{2+}\) indicates that the overall charge is +2. Since water (H2O) is a neutral ligand, the oxidation state of iron must be +2.

### Step 2: Write the electron configuration of iron
The atomic number of iron (Fe) is 26. The electron configuration of neutral iron is:
\[ \text{[Ar]} \, 3d^6 \, 4s^2 \]
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