Thomson's Gold Foil Experiment

At the end of the nineteenth century, scientists believed that all matter was composed of atoms. However, an English physicist named J.J. Thomson (1856-1940) discovered an even smaller particle that he called corpuscles, although we know them as electrons today. Thomson discovered that electrons are negatively charged, that they are much smaller and have less mass than atoms, and that they are uniformly present in many different types of substances. With this new discovery, the question of a balancing positive charge arose. Atoms are known to be charge-neutral, so it was believed that they must contain a positive charge that balanced the negative charge of the electron. Thomson proposed that the electrons, which are negatively charged, were small particles contained within a positively charged sphere. The model of this was known as the plum pudding model. In 1909, Ernest Rutherford (1871-1937), who worked under J.J. Thomson, overturned Thomson's model with the well-known gold foil experiment in an attempt to confirm it. Rutherford concluded that matter must not be as uniform as previously assumed but rather, it contains large regions of empty space dotted with small regions of very dense matter. With his experiment Rutherford observed that the mass and positive charge of an atom must all be concentrated in a space much smaller …show more content…
This idea helped him develop the nuclear theory of the atom, which has three (3) basic parts:More work by Rutherford and others that wad completed later on demonstrated that the atom's nucleus contains both positively charged protons and