Flame Emission Spectroscopy

• When metal ions are heated they emit light. The wavelengths of the light a specific to that particular metal ion. Unlike flame tests, flame emission spectroscopy detects the individual wavelengths that are emitted using a spectroscope.
• Every different metal ion produces a different pattern of wave lengths. So they all produce a unique line spectrum.
• The intensity of the lines indicates the concentration of the ion.
• The main advantage of flame emission spectroscopy is that if a sample contains multiple different metal ions, the spectrum will show the lines for all of them. For example, you can see both A and B's line spectrums here:

  
• If we have an unknown sample we can use the patterns of known metal ions to determine what is in the sample. They can also calculate the concentration of each ion.

  
• Flame test vs Flame emission spectroscopy is a good comparison of manual tests (normally basic and cheap) vs instrumental methods (use expensive machines but often give better results)
• The 3 main benefits of instrumental methods are:

  Very accurate

  Very sensitive

  Very fast
• 1. First, metal ions are heated until they emit light.
  2. The light is detected by a spectroscope which can distinguish between the individual wavelengths of light emitted.
  3. As each metal ion emits a unique combination of wavelengths it will produce a unique line spectrum.
  4. This allows us to identify an unknown metal cation by comparing its line spectrum to those of known metal cations in a data bank.