Question

Explain effective atomic number (EAN).

Hint:

The EAN helps to predict the stability of transition metal complexes and is particularly useful for complexes following the 18-electron rule.

Answer 1

Step 1: Definition of Effective Atomic Number (EAN).
The effective atomic number (EAN) is the total number of electrons around a metal ion in a coordination complex, including the electrons donated by the ligands. It is used to assess the stability of transition metal complexes, particularly when the metal follows the 18-electron rule, which is a guideline for predicting the stability of organometallic compounds.
Step 2: Calculation of EAN.
The effective atomic number is calculated as: \[ \text{EAN} = \text{Atomic number of the metal ion} - \text{Oxidation state of the metal} + \text{Number of electrons donated by ligands} \]
Step 3: Example.
For the complex \([Ni(CO)_4]\), Ni is in the zero oxidation state, and each CO ligand donates two electrons. The EAN of Ni in this complex would be: \[ \text{EAN of Ni} = 28 - 0 + (4 \times 2) = 28 + 8 = 36 \]