Formula Using Roman Numerals - National 5 Chemistry Revision

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In this guide

  1. Revise
  2. Test
  1. Formula from names of compounds
  2. Valency
  3. Formulae of compounds containing group ions
  4. Formula using Roman numerals

Formula using Roman numerals

Some elements, particularly the transition metals, do not always have the same valency in their different compounds. The valency of these elements is usually given in roman numerals inside brackets.

Roman NumeralNumber
IOne
IITwo
IIIThree
IVFour
VFive
VISix
Roman NumeralI
NumberOne
Roman NumeralII
NumberTwo
Roman NumeralIII
NumberThree
Roman NumeralIV
NumberFour
Roman NumeralV
NumberFive
Roman NumeralVI
NumberSix

Example

What is the formula for copper (I) oxide?

Copper 1 has a valency of one. Oxygen has a valency of 2. The formula is CuO2.

Ions are electrically charged particles that form when atoms lose or gain electrons.

Next upTest your understandingPrevious pageFormulae of compounds containing group ions

More guides on this topic

  • Revise: Rates of reaction
  • Revise: Atomic structure
  • Revise: Bonding and properties of materials
  • Revise: Balanced equations
  • Revise: The mole and concentration of solutions
  • Revise: Acids and bases
  • Video playlist

Related links

  • BBC Science
  • BBC News: Science
  • BBC Lab UK
  • SQA National 5 Chemistry
  • School Science
  • Royal Society of Chemistry
  • Creative Chemistry

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