Structure of the atom

• • an atom has a central nucleus
  • this is surrounded by electrons arranged in shells
• Nucleus compared to atom

  • the radius of an atom is about 0.1nm (1 × 10-10 m)
  • the radius of a nucleus (1 × 10-14 m) is less than 1/10000 of the radius of an atom
• Subatomic particles

  • the nuclei of all atoms contain subatomic particles called protons
  • the nuclei of most atoms also contain neutrons
  • the masses of subatomic particles are very tiny
• Relative mass


  the number of times heavier a particle is, compared to another
• Proton

  • relative mass = 1
  • relative charge = +1
• Neutron

  • relative mass = 1
  • relative charge = 0
• Electron

  • relative mass = very small
  • relative charge = -1