flame tests

• lithium - crimson
• sodium - yellow
• potassium - lilac
• calcium - orange-red
• copper - green
• problems:

  -difficult to distinguish especially when there is a low concentration of the metal compound

  -sometimes a sample contains a mixture of metal ions masking the colour of the flame
• flame emission spectroscopy:

  -sample of metal ion in solution is placed into a flame

  -light given out is then passed into a machine called a spectroscope

  -spectroscope converts the light into a line spectrum

  -positions of the lines in the spectrum are specific for a given metal ion

  -therefore we can identify the metal ion in the sample
• flame emission spectroscopy can tell us the concentration of the metal ion as the lines become more intense as the concentration of the metal ion increases
• flame emission spectroscopy is an example of an instrumental method
• instrumental methods:

  -rapid analysis of samples

  -sensitive so will work with even a small sample of a metal compound

  -accurate, more likely to identify a metal ion correctly than using a flame test