Question

What is EAN for metal ion in \([\text{Fe(CN)}_6]^{3-}\) ?

• A. \(37\)
• B. \(36\)
• C. \(35\)
• D. \(34\)

Hint:

EAN = atomic number of metal minus oxidation state plus 2 times the number of ligands.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Effective atomic number (EAN) is the total number of electrons around the central metal, counting the electrons donated by ligands.

Step 2: Key Formula or Approach:
\[ \text{EAN} = Z - (\text{oxidation state}) + 2\times(\text{number of ligands}) \]
Each cyanide ion donates one pair, so 2 electrons.

Step 3: Detailed Explanation:
In \([\text{Fe(CN)}_6]^{3-}\), the oxidation state of Fe is: \(x + 6(-1) = -3\), so \(x = +3\).
Fe has Z = 26.
\[ \text{EAN} = 26 - 3 + 2\times6 = 23 + 12 = 35 \]
Option (B) 36 is the EAN of \([\text{Fe(CN)}_6]^{4-}\) with \(\text{Fe}^{2+}\), where \(26 - 2 + 12 = 36\), the krypton configuration. For the \(+3\) ion the value is one less.

Final Answer:
The EAN of iron in \([\text{Fe(CN)}_6]^{3-}\) is 35, option (C). \[ \boxed{35 \text{ (C)}} \]