Mass Spectrometer

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Mass Spectrum -(Eg. Magnesium)

A sample of magnesium vapour is fed into a mass spectrometer and is bombarded by high energy electrons in the ionisation region. These electrons knock off electrons from the magnesium to produce magnesium ions (Mg+)

Mg-> Mg+ + e-

Some magnesium atoms are hit by electrons with very high energy levels so they lose 2 electrons to produce Mg2+

These charged magnesium ions are passed through the spectrometer and are sped up by an electric field- this gives all ions with the same charge the same kinetic energy. They pass through the drift region, magnesium has 3 isotopes so magnesium 24 will hit the ion detector in a shorter time then the heavier ions. The flight time will be less.

On a mass spectrum graph there would be three lines. On the y-axis is the percentage abundance in the sample and the x-axis is the mass/ charge ratio.