Identifying Ions

Specification Point 9.2C:
  • Describe flame tests to identify the following ions in solids:
    a) lithium ion, Li+ (red)
    b) sodium ion, Na+ (yellow)
    c) potassium ion, K+ (lilac)
    d) calcium ion, Ca2+ (orange-red)
    e) copper ion, Cu+ (blue-green)
  • Metal ions produce a colour if heated strongly in a flame.
  • Ions from different metals produce different colours.
  • The flame test is thus used to identify metal ions by the colour of the flame they produce.
  • Dip the loop of an unreactive metal wire such as nichrome or platinum in dilute acid and rinse with distilled water.
  • This cleans the wire loop and avoids contamination. This is an important step as the test will only work if there are just one type of ion present.
  • Two or more ions means the colours will mix, making identification difficult and erroneous.
  • Dip the loop into the solid sample and place it in the edge of the blue Bunsen flame.

Performing a Flame Test, Edexcel GCSE Chemistry

Diagram showing the technique for carrying out a flame test

  • The colour of the flame is observed and used to identify the metal ion present.

Flame Test Colours, Edexcel GCSE Chemistry

The colours formed in the flame test for metal ions

Flame test table, Edexcel GCSE Chemistry

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Edexcel GCSE Chemistry Notes

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Morgan Curtin Chemistry

Author: Morgan

Morgan’s passion for the Periodic Table begun on his 10th birthday when he received his first Chemistry set. After studying the subject at university he went on to become a fully fledged Chemistry teacher, and now works in an international school in Madrid! In his spare time he helps create our fantastic resources to help you ace your exams.