Write the formula of the following coordination compound: Iron(III) hexacyanoferrate(II)

The formula of the complex anion hexacyanoferrate(II) is [Fe(CN)₆]⁴⁻. The oxidation number of iron is +2 and each cyanide ion has -1 charge. Hence, the net charge on the complex anion is +2 + 6(-1) = -4. A -4 charge on the complex anion will be balanced by +3 charge on Fe³⁺ cation when 4 Fe³⁺ cations combine with 3 [Fe(CN)₆]⁴⁻ complex anions. The formula of the coordination compound Iron(III) hexacyanoferrate(II) is Fe₄([Fe(CN)₆]₃. Note: In the name Iron(III) hexacyanoferrate(II), the numbers in parenthesis in roman numerals indicate the oxidation number of iron atoms.