Mass Spectrometer

The abundance of isotopes are determined using a Mass Spectrometer.

The Process

1. Atoms vaporised, and sent into spectrometer.
2. Heated tungsten wire produces electrons, which “knock electrons” from the sample, providing ions with a positive charge.
3. Particles are accelerated using an electric field.
4. A Magnetic field is placed 90^o to the tube, the particles move; they are deflected.
5. The larger particles are deflected least, and the lighter particles most.
6. The number of ions hitting the detector is measured, and the magnetic field is changed so that the different isotopes can hit the detector. This gives an abundance of each separate isotope.

The results

• The mass spectrometer is used to measure the abundances of the isotopes of an element.
• The results are in the form of a line graph, with the mass/charge on the x-axis, and the abundance up the y-axis.
  • The Graph shows the abundance of ³⁵Cl within the gas was 75%, and ³⁷Cl was 25%.

  Useful books for revision:

  Revise AS Chemistry for Salters (Written by experienced examiners and teachers of Salter's chemistry)
  Revise AS Chemistry for Salters (OCR) (Salters Advanced Chemistry)
  
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