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 straight through

  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 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
• Positive charge in nucleus is due to positive particles called protons