Effective Atomic Number of K₃FeCl₆
Effective atomic number is a concept used in coordination chemistry to account for the different electron configurations of transition metal complexes. In the case of K₃FeCl₆, we need to calculate the effective atomic number of the central metal ion, Fe.

Calculation of Effective Atomic Number
To calculate the effective atomic number of Fe in K₃FeCl₆, we need to consider the oxidation state of Fe and the ligands surrounding it. In this complex, Fe is in the +3 oxidation state and is surrounded by six chloride ions (Cl^-) and three potassium ions (K⁺).
The effective atomic number can be calculated using the formula:
EAN = Z - s
Where:
- Z is the atomic number of the metal ion (Fe)
- s is the number of electrons donated by the ligands

Calculation for Fe in K₃FeCl₆
For Fe in the +3 oxidation state, the atomic number is 26. Each chloride ion donates one electron, and each potassium ion donates one electron. Therefore, the total number of electrons donated by the ligands is 6 (from Cl^-) + 3 (from K⁺) = 9.
EAN = 26 - 9
EAN = 17
Therefore, the effective atomic number of Fe in K₃FeCl₆ is 17. This means that Fe behaves as if it has 17 electrons in the complex, taking into account the electron donation by the surrounding ligands.