2.1 The nuclear atom


  • Atoms consist of a three subatomic particles
    • Proton
    • Neutron
    • Electron


  • Atomic Number Z: number of protons in the nucleus of an atom of an element.
  • Mass Number A: number of protons + number of neutrons
  • Relative atomic mass Ar: Ratio of the average mass of the atom to the unified atomic mass unit

Nuclear Symbol

  • Atomic Mass Units (AMU): 1/12th of the mass of a carbon – 12 atom in its ground state. This is used to express masses of atomic particles.
    • 1 AMU = 1.6605402 x 10-27 kg

The mass spectrometer

  • The mass spectrometer is an instrument used to determine the relative atomic mass Ar of an element by using its isotopes.
  • Watch this video

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