Rutherford Scattering (AQA GCSE Combined Science: Trilogy: Physics): Revision Note

Rutherford Scattering

Alpha Scattering

• In 1909 a group of scientists were investigating the Plum Pudding model

  • Physicist, Ernest Rutherford was instructing two of his students, Hans Geiger and Ernest Marsden to carry out the experiment

• They were directing a beam of alpha particles (He²⁺ ions) at a thin gold foil

• They expected the alpha particles to travel through the gold foil, and maybe change direction a small amount

• Instead, they discovered that :

  • Most of the alpha particles passed straight through the foil

  • Some of the alpha particles changed direction but continued through the foil

  • A few of the alpha particles bounced back off the gold foil

• The bouncing back could not be explained by the Plum Pudding model, so a new model had to be created

When alpha particles are fired at thin gold foil, most of them go straight through, some are deflected and a very small number bounce straight back

The Nuclear Model

• Ernest Rutherford made different conclusions from the findings of the experiment

• The table below describes the findings and conclusions of A, B and C from the image above:

Alpha Scattering Findings and Conclusions Table

• Rutherford proposed the nuclear model of the atom

• In the nuclear model:

  • Nearly all of the mass of the atom is concentrated in the centre of the atom (in the nucleus)

  • The nucleus is positively charged

  • Negatively charged electrons orbit the nucleus at a distance

• Rutherford’s nuclear model replaced the Plum Pudding model

  • The nuclear model could explain experimental observations better than the Plum Pudding model

The Nuclear model replaced the Plum Pudding model as it could better explain the observations of Rutherford’s Scattering Experiment