ean rule

Question

Effective atomic number (EAN) of Co in [Co(NO2)(NH3)5]2+ (atomic number of Co = 27) is:

RankGuru · Accepted Answer

1. **Formula**: $EAN = Z - (	ext{Oxidation State}) + (	ext{Donated electrons from ligands})$.
2. **Oxidation State ($OS$)**:
   - Let $Co$ be $x$. $NO_2$ is $-1$. $NH_3$ is $0$.
   - $x + (-1) + 5(0) = +2 \implies x = +3$.
3. **Ligand Donation**:
   - One $NO_2^-$ donates $2$ electrons.
   - Five $NH_3$ donate $5 	imes 2 = 10$ electrons.
   - Total donation $= 12$ electrons.
4. **Calculation**: $EAN = 27 - 3 + 12 = 24 + 12 = 36$.
5. **Significance**: An EAN of $36$ matches the noble gas configuration of Krypton, suggesting high stability.

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The effective atomic number (EAN) of Fe in [Fe(CN)₆]⁴⁻ is: