Writing formulas and IUPAC names sheet3-mark answer frameWrite the IUPAC names of the following and state the oxidation state of the metal: (i) [CoCl₂(en)₂]Cl (ii) K₃[Fe(CN)₆] (iii) [Ni(CO)₄].
How to lay out the answer. Follow the frame, then write it in your own words.
- 1 · Find each oxidation state first.
- (i) x − 2 + 0 = +1, so +3
- (ii) x − 6 = −3, so +3
- (iii) x + 0 = 0, so 0
- 2 · Decide: cation, anion or neutral. (i) complex cation (ii) complex anion, so the metal takes -ate (iii) neutral molecule.
- 3 · Order the ligands and add prefixes. (i) dichlorido, then bis(ethane-1,2-diamine) (ii) hexacyanido (iii) tetracarbonyl.
- 4 · Write the names.
- (i) dichloridobis(ethane-1,2-diamine)cobalt(III) chloride
- (ii) potassium hexacyanidoferrate(III)
- (iii) tetracarbonylnickel(0)
- 5 · Check the spelling. ammine, chlorido, cyanido; the Roman numeral in brackets with no space before it.
Scoring tip: Work out the oxidation state before you write anything. It also tells you whether the metal needs the -ate ending.
