Rutherford Scattering - A Level Standard Questions


(a) Describe the principal features of the nuclear model of the atom suggested by Rutherford.

  • nucleus is small
  • nucleus is massive Massive does not mean 'big' in this case - it mean it contains most of the mass
  • nucleus is positive
  • electrons surround the nucleus
  • electrons are negative (or electrons have small mass)

(5 marks)

(b) When gold foil is bombarded by alpha particles it is found that most of the particles pass through the foil without significant change of direction or loss of energy. A few particles are deviated from their original direction by more than 90°. Explain, in terms of the nuclear model of the atom and by considering the nature of the forces acting,

(i) why some alpha particles are deflected through large angles,

Some alpha particles approach the (gold) nucleus so that their path takes them very near to it. The gold nucleus and alpha particle are both positively charged therefor ethere is a repulsive force between the (gold) nucleus and the alpha particle. This causes the alpha particle to be deflected througha large angle.

(ii) why most of the alpha particles pass through the foil without any significant change in direction.

The space between neighbouring (gold) nuclei is very large large [or the atom is mostly empty space]. The coulomb repulsion depends on an inverse square relationship, therefore the further apart the alpha particle and gold nucleus are, the smaller the repulsive force they will experience, and the less affected the path of the alpha particle wil be.Therefore most alpha particles do not approach nuclei close enough to be (significantly) deflected

(5 marks MAX)

(Total 10 marks)