Development of the model of the atom

• Atomic


  Relating to the structure and properties of atoms
• Atomic structure


  • Everything made up of tiny particles
  • Particles can't be broken down any further
  • Particles separated from each other by empty space
• Atomic theory


  Everything is made up of tiny particles
• Democritus proposed the idea of atoms

  5th century BC
• John Dalton proposed atoms as solid spheres


  1800s
• Dalton's atomic model


  • Different types of spheres make up different elements
• J.J. Thomson proposed the plum pudding model


  1897
• Thomson's plum pudding model

  • Atoms could not be solid spheres
  • Atoms contain negatively charged particles
  • Atoms have a general ball of positive charge with discrete electrons stuck in it
• Rutherford's gold foil experiment


  1909
• Rutherford's gold foil experiment

  1. Alpha particles fired at gold foil

  2. Most passed through, some deflected to the side or back

  3. Proved Thomson's model was wrong
• Rutherford's nuclear model


  • Atoms have a compact nucleus containing positive charge
  • Negative charge 'cloud' around the nucleus
  • Nothing stopping the atom from collapsing
• Bohr proposed his model of the atom

  1913
• Bohr's model of the atom

  • Electrons orbit the nucleus in fixed shells
  • Electrons can only exist in certain allowed energy levels
• Rutherford discovered protons
• Chadwick discovered neutrons
• The current model of the atom is pretty much the same as Rutherford's model