2.1 The nuclear atom

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 A_r: Ratio of the average mass of the atom to the unified atomic mass unit

• 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 A_r of an element by using its isotopes.
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