Answer to Question #300787 in Atomic and Nuclear Physics for J.m

Question

Discuss Thomson’s atomic model ( what was his proposal on how an atom looks like?).

Explain its failures.

Answer 1

J. J. Thomson proposed a model also called "plum pudding". In such a model electrons are surrounded by a volume of positive charge, so the net electric charge of atom is zero. At that time the electrons had been already discovered, but the nucleus hadn't, so the distribution of the positive charge was unknown.

However, this model turned to be unrealistic when Rutherford performed experiments on the scattering of alpha-particles on golden foil. It turned out that atoms have a small positively charged nuclei. So the planetary model of atoms was suggested.