alpha scattering and the nuclear model

• Atom


  Tiny sphere that cannot be divided
• In 1897, scientists discovered that atoms contain tiny negative particles called electrons
• Plum pudding model


  Atom is a ball of positive charge with negative electrons embedded in it
• Alpha scattering experiment


  1. Fired alpha particles at gold foil

  2. Most alpha particles passed through without changing direction

  3. Some alpha particles were deflected

  4. Some alpha particles bounced straight back
• Results of alpha scattering experiment

  • Atoms are mainly empty space
  • Center of atom has positive charge that repelled alpha particles
  • Mass of atom is concentrated in the center
• Nuclear model


  Most of the atom is empty space, with a tiny positive nucleus containing almost all the mass, and negative electrons orbiting the nucleus
• Electron energy levels/shells


  Electrons orbit the nucleus at specific distances
• Proton


  Positive particle in the nucleus
• Neutron


  Neutral particle in the nucleus
• The nuclear model replaced the plum pudding model
• The nuclear model was proposed by scientist Neil Bohr
• The discovery of the neutron was made by scientist James Chadwick