In the complex ion [Fe(NH_3)_2Br_4]^{2-}, what is the oxidation state (charge) of the iron (Fe) atom? (Omit the + sign in your answer.)

• A. 2
• B. 3
• C. 6
• D. 4

Answer: (D)

Verified step by step guidance

1. Identify the overall charge of the complex ion, which is given as 2- (i.e., the charge on [Fe(NH_3)_2Br_4]^{2-} is -2).
2. Determine the charges of the ligands: NH_3 (ammine) is a neutral ligand with a charge of 0, and Br^- (bromide) is a monodentate ligand with a charge of -1 each.
3. Set up an equation to represent the sum of the oxidation state of Fe (let it be x) plus the charges contributed by the ligands equal to the overall charge of the complex ion:
4. \[ x + 2(0) + 4(-1) = -2 \]
5. Simplify the equation to solve for x:
6. \[ x - 4 = -2 \]
7. Solve for x to find the oxidation state of Fe: