The atom — Describe

Describe how the alpha-particle scattering experiment (firing alpha particles at thin gold foil) supports the nuclear model of the atom.

A beam of alpha particles was directed at a sheet of thin metal (gold) foil and the scattering angles observed. (a) Most alpha particles passed straight through the foil with little or no deflection, showing that the atom is mostly empty space and that the nucleus is very small compared to the size of the whole atom. (b) A small number of alpha particles were deflected through large angles, and a few bounced almost straight back. Since alpha particles are relatively fast and massive, only a very massive object could cause such large deflections, showing that the nucleus contains most of the mass of the atom concentrated in a tiny volume. (c) The fact that (positively charged) alpha particles were repelled/deflected at all, especially through large angles, shows that the nucleus itself is positively charged, since like charges repel.