Effective Atomic Number (EAN Rule)

Formula:

$$\text{EAN} = Z - \text{(Oxidation State)} + 2 \cdot \text{(Coordination Number)}$$

Concept: Calculates the total number of electrons surrounding a central metal atom or ion in a complex to determine if it achieves the stable electronic configuration of a noble gas.

Notation:

• $$\text{EAN}$$ = Effective Atomic Number;
• $$Z$$ = Atomic number of the central metal;
• $$\text{Oxidation State}$$ = Net charge on the metal center;
• $$\text{Coordination Number}$$ = Total electron pairs accepted from donor ligands.