Given the complex ion [Fe(CN)_6]^{4-}, what is the oxidation number of iron (Fe) in the complex?

• A. +4
• B. +2
• C. 0
• D. +3

Answer: (B)

Verified step by step guidance

1. Identify the overall charge of the complex ion, which is given as \$4-\( for \)[\text{Fe}(\text{CN})_6]^{4-}$.
2. Recognize that the cyanide ligand (CN) is a monodentate ligand with a charge of \(-1\) each.
3. Calculate the total charge contributed by the six cyanide ligands: \$6 \times (-1) = -6$.
4. Set up an equation for the sum of the oxidation number of iron (let it be \(x\)) and the total charge from the ligands equal to the overall charge of the complex: \(x + (-6) = -4\).
5. Solve the equation for \(x\) to find the oxidation number of iron: \(x = -4 + 6\).