The Atom

• Atoms consist of nucleus and electrons
• Nucleus: central part of atom made of protons (positively charged) and neutrons. These two types of particles are called nucleons. They are bound together by the strong nuclear force
• Electrons: almost mass-less particles which orbit nucleus in shells
• Proton number: number of protons in an atom
• Nucleon number: the number of nucleons (protons + neutrons) in an atom
• Rutherford's gold foil experiment showed that the atom is mostly empty space with a tiny, dense, positively-charged nucleus.
• The nuclide notation for atoms has:

  • nucleon number
  • proton number
  • element symbol

  
• Isotopes are atoms of the same element that have different numbers of neutrons
• Some isotopes of atoms are radioactive, some are non-radioactive
• Radio isotopes are unstable atoms, which break down giving radiation
• Radio isotopes can be used for:

  • radiotherapy for cancer cells
  • industry: radioisotopes added to oil/gas to detect leaks with geiger counters
  • archaeological use: can be used for carbon dating