Question:medium

Calculate effective atomic number of \( Fe^{2+} \) in \( [Fe(CN)_6]^{4-} \) [ Given : (Z = 26) ]

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If the EAN equals 18, 36, 54, or 86, the complex is said to follow the EAN rule, indicating high stability.
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Solution and Explanation

Step 1: Understanding the Concept:
Effective Atomic Number (EAN) is the total number of electrons surrounding the central metal atom/ion in a complex.
Step 2: Key Formula or Approach:
\[ EAN = Z - X + Y \]
Where:
\(Z = 26\) (Atomic number)
\(X = 2\) (Oxidation state of \(Fe\))
\(Y = 2 \times 6 = 12\) (Electrons donated by 6 cyanide ligands)
Step 3: Detailed Explanation:
1. Oxidation state of \(Fe\): \(x + 6(-1) = -4 \Rightarrow x = +2\).
2. Electrons in \(Fe\) atom = 26.
3. Electrons in \(Fe^{2+}\) ion = \(26 - 2 = 24\).
4. Electrons donated by 6 \(CN^-\) ligands = \(6 \times 2 = 12\).
5. \(EAN = 24 + 12 = 36\).
Since 36 is the atomic number of the noble gas Krypton (\(Kr\)), this complex is very stable.
Step 4: Final Answer:
The EAN of Iron in the complex is \(36\).
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