The Emission Spectrum
- Flame emission spectroscopy is a technique used to analyse metal ions in solution
- When substances are heated they often emit energy in the form of light
- This is due to electrons falling back to their original energy levels after becoming excited which causes them to jump up one or more energy levels
- Flame emission spectroscopy works by exposing the sample to a very hot flame and then measuring the intensity and wavelength of the light emitted
- The output is an emission spectrum in which different elements produce lines in different parts of the spectrum
Diagram of an emission spectrum for mercury obtained from flame photometry
- The emission spectrum consists of brightly coloured thin lines on a dark background and each element ion produces a unique spectrum
- Flame emission spectroscopy also works for mixtures of ions
- This is a major advantage over flame testing which can only analyze one ion at a time
- The intensity of the light produced is proportional to the number of ions vaporised, so the technique can be used to determine the concentration of metal ions in a solution by reference to a standard solution of known concentration