IB Chemistry SL

Revision Notes

9.1.4 Naming Transition Metal Compounds

Naming Transition Metal Compounds

  • Transition metals are characterized by having variable oxidation numbers.
  • Oxidation numbers can be used in the names of compounds to indicate which oxidation number a particular element in the compound is in
  • Where the element has a variable oxidation number, the number is written afterwards in Roman numerals.
  • This is called the STOCK NOTATION (after the German inorganic chemist Alfred Stock), but is not widely used for non-metals, so SO2 is sulphur dioxide rather than sulphur(IV) oxide
  • For example, iron can be both +2 and +3 so Roman numerals are used to distinguish between them
    • Fe2+ in FeO can be written as iron(II) oxide
    • Fe3+ in Fe2O3 can be written as iron(III) oxide

Worked Example

Can you name these transition metal compounds?

  1. Cu2O
  2. MnSO4
  3. Na2CrO4
  4. KMnO4
  5. Na2Cr2O7


Answer 1: copper(I) oxide:

The ox. no. of 1 O atom is -2 and Cu2O has overall no charge so the ox. no. of Cu is +1

Answer 2: manganese(II) sulfate:

The charge on the sulfate ion is -2, so the charge on Mn and ox. no. is +2

Answer 3: sodium chromate(VI):

The ox. no. of 2 Na atoms is +2 so CrO4 has an overall -2 charge, so the ox. no. of Cr is +6

Answer 4: potassium manganate(VII):

The ox. no. of a K atom is +1 so MnO4 has overall -1 charge, so the ox. no. of Mn is +7

Answer 5: sodium dichromate(VI):

The ox. no. of 2 Na atoms is +2 so Cr2O7 has an overall -2 charge, so the ox. no. of Cr is +6. To distinguish it from CrO4 we use the prefix di in front of the anion

Exam Tip

The answer to No. 2 should strictly speaking being managanese(II) sulfate (VI) since  sulfur is an element with a variable oxidation number. However, it is a common ion whose name and formula you should know and you are only required to name transition metal compounds using Stock Notation


Join Save My Exams

Download all our Revision Notes as PDFs

Try a Free Sample of our revision notes as a printable PDF.

Join Now
Already a member?
Go to Top