Rutherford scattering (3 marks)

In the alpha-particle scattering experiment, most alpha particles passed straight through the gold foil but a small number were deflected through large angles, and a very few bounced almost straight back. Explain what each of these three observations tells us about the structure of the atom.

Mark scheme (3 marks — 1 each):

• Most pass straight through → atom is mostly empty space.
• A small number are deflected → there is a concentrated positive charge in the atom (like charges repel).
• A very few bounce back → the positive charge / mass is concentrated in a tiny, dense nucleus.

Credit: explicit reference that this disproved the plum-pudding model and led to the nuclear model (Rutherford, 1911).