Mass spectrometer and relative atomic mass

Mass spectrometer and relative atomic mass

1. Mass spectrometer

   • Relative atomic masses can be determined using a mass spectrometer
   • A vaporized sample is injected into the instrument
   • Atoms of the element are ionized by being bombarded with a stream of high energy electrons in the ionization chamber
   • In practice the instrument is set so that only ions with a single positive charge are formed.
   • The resulting unipositive ions pass through holes in parallel plates under the influence of an electric field where they are accelerated
   • The ions are then deflected by an external magnetic field.
   • The amount of deflection depends both on the mass of the ion and its charge
   • The smaller the mass and the higher the charge the greater the deflection.
   • Ions with a particular mass/charge ratio are then recorded on a detector which measures both the mass and the relative amounts of all the ions present.

2. isotopes of elements are radioactive as the nuclei of these atoms break down spontaneously.