Flame Emission Spectroscopy (AQA GCSE Chemistry)

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Flame emission spectroscopy

  • Flame emission spectroscopy is an example of an instrumental method used to analyse metal ions in solution

How does flame emission spectroscopy work?

  • The sample is put into a flame 
  • The light given out is passed through a spectroscope 
  • The intensity and wavelength of the light emitted is measured
  • The output is a line spectrum in which different elements produce lines in different parts of the spectrum
  • The spectrum can be analysed to identify the metal ions in the solution and their concentrations
  • Flame emission spectroscopy also works for mixtures of ions
  • This is a major advantage over flame testing which can only analyse one ion at a time

flame emission spectrum

A line spectrum from flame emission spectroscopy

Using reference data

  • Ions in unknown samples can be identified by comparing the sample spectrum to reference spectra
  • This is particularly useful if the sample contains a number of different ions
  • The following flame spectrum for example was obtained for a solution containing an unknown metal:

flame emission spectrum of unknown metal

Flame spectrum for an unknown metal 

  • When compared to the reference spectra below we can see that the solution must contain sodium ions:

flame emission spectrum of different elements

Diagram of a reference spectra including an emission spectrum for sodium

Examiner Tip

By comparison with the emission spectrum of the sample, reference spectra allow us to quickly identify ions and mixtures of ions.

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Stewart

Author: Stewart

Expertise: Chemistry Lead

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Exam Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.