Flame test colours for the five metal ions
A flame test identifies some metal ions by the colour they give a flame. Sodium gives yellow, potassium gives lilac and calcium gives orange-red on both AQA and Edexcel. The two boards word the other two colours differently. AQA calls the lithium flame crimson, and Edexcel calls it red. AQA calls the copper flame green, and Edexcel calls it blue-green.
The five colours, board by board
The chart shows each ion with the colour word from each board. Here are the same results as a list:
- Lithium ion, Li⁺: crimson (AQA), red (Edexcel)
- Sodium ion, Na⁺: yellow (AQA and Edexcel)
- Potassium ion, K⁺: lilac (AQA and Edexcel)
- Calcium ion, Ca²⁺: orange-red (AQA and Edexcel)
- Copper ion, Cu²⁺: green (AQA), blue-green (Edexcel)
OCR Gateway (J248) and OCR Twenty First Century (J258) name the same five ions. Neither OCR specification prints a colour word for any of them. If you sit OCR, ask your teacher which words they expect.
Where the boards use different words
Lithium and copper are the two ions where AQA and Edexcel disagree on the word. Crimson is a deep red, so both boards describe a red flame for lithium. For copper, Edexcel adds blue to the green. In your answers, use the word your own board prints.
Lithium and calcium are the easiest pair to confuse. Both give a reddish flame. Calcium's colour is orange-red, so look for the orange tint.
What the test can and cannot show
A flame test picks out the metal ion in a compound. Metal ions are positive ions, also called cations. They form when metal atoms lose electrons, which the page on ionic bonding explains.
The test works best on a sample with one metal ion. AQA warns that in a mixture of ions, one flame colour can hide another. It also says the colours of other metal ions are not needed. Edexcel describes flame tests on ions in solids.
Instruments can do the same job. OCR Gateway asks you to describe their advantages, which it gives as sensitivity, accuracy and speed. Edexcel asks you to read data from a flame photometer, a machine that measures the light from a flame. You use it to find the concentration of an ion from a calibration curve, or to name an ion by matching reference data.
Which courses include flame tests
Flame tests belong to separate chemistry only. AQA puts them in GCSE Chemistry (8462), and they are missing from Combined Science: Trilogy (8464). Edexcel puts them in GCSE Chemistry (1CH0), and Combined Science (1SC0) leaves them out. Both OCR specifications mark them as separate science content. KS3 science does not include flame colours.
Flame tests sit beside other ion tests in the same topic. For tests using sodium hydroxide, the boards pick different metal ions. AQA is the only board with magnesium. Edexcel is the only one with the ammonium ion, and OCR is the only one with zinc. The gas tests are in every course, and you can find them on the page of tests for gases.
Common mistakes
- Mixing up lithium and calcium. Both flames look red, and calcium's has an orange tint.
- Writing one board's colour word in another board's exam. Edexcel says blue-green for copper where AQA says green.
- Testing a mixture and expecting every colour to show. One colour can mask another.
- Thinking a flame test names the whole compound. It shows only the metal ion.
Identify the ion from the flame in Flame Test Lab. The chemistry hub lists the other pages in this set, and the periodic table shows where each of these metals sits.
Questions people ask
What colour does sodium give in a flame test?
Yellow. AQA and Edexcel both use that word for the sodium ion.
Is the lithium flame red or crimson?
It depends on your board. AQA prints crimson and Edexcel prints red. Both words describe a red flame.
Are flame tests in GCSE Combined Science?
No. AQA 8464 and Edexcel 1SC0 do not include them, and OCR marks them as separate chemistry content. You meet them if you take GCSE Chemistry.