Unit 4: atomic structure

• Atom


  Positively charged nucleus (which contains neutrons and protons) surrounded by negatively charged electrons
• Subatomic Particles


  • Proton
  • Neutron
  • Electron
• Relative Mass


  • Proton: 1
  • Neutron: 1
  • Electron: 0 (0.0005)
• Relative Charge


  • Proton: +1
  • Neutron: 0
  • Electron: -1
• Typical radius of an atom: 1 × 10−10 metres
• The radius of the nucleus is 10 000 times smaller than the radius of the atom
• Most (nearly all) the mass of the atom is concentrated at the nucleus
• Electron Arrangement


  Electrons lie at different distances from the nucleus (different energy levels). The electron arrangements may change with the interaction with EM radiation
• Isotopes


  Atoms of the same element, but with different masses, which have the same number of protons but different number of neutrons
• Elements


  All atoms of the same element have the same number of protons
• Neutral atoms


  Have the same number of electrons and protons