mass spec

• What is meant by an isotope?

  Isotopes are atoms of the same element with different numbers of neutrons and different masses.
• Why do isotopes of an element react in the same way?

  Because they all have the same electron configuration.
• What does the term abundance refer to in the context of isotopes?

  Abundance tells us how common each isotope is.
• What machine is used to determine the mass number and abundance of isotopes?

  A mass spectrometer is used for this purpose.
• What type of mass spectrometer is required for the AQA specification?

  The time-of-flight mass spectrometer is required for the AQA specification.
• What are the main stages of how a time-of-flight mass spectrometer works?

  1. Sample is placed in the sample chamber.
  2. Ionization converts atoms into positive ions.
  3. Ions are accelerated towards a negatively charged plate.
  4. Ions drift down the chamber at different velocities.
  5. Ions reach the detector, causing a current to flow.
• Why is the interior of the mass spectrometer a vacuum?

  To prevent the ions from colliding with molecules in the air.
• How can you interpret a mass spectrum for an element?

  • Identify the number of peaks to determine the number of isotopes.
  • The y-axis shows relative abundance as a percentage.
  • The x-axis shows the m/z ratio (mass to charge ratio).