1911 - British scientist Ernest Rutherford experimented on the plum pudding theory of the atom, in attempts to prove this theory incorrect. He tested this by firing a direct beam of alpha particles at a thin sheet of gold foil, which was surrounded by a fluorescent screen. In doing this, any particles that were deflected by the gold foil would be obvious, as they would show as a flash on the fluorescent screen. If the plum pudding model had been correct, all of the alpha particles would have travelled straight through the gold foil, with no deflections. However, this did not occur. Most of the alpha particles went straight through the gold foil, as expected, yet a small amount of alpha particles were deflected as they passed through the foil, and an even fewer amount were deflected straight back off the foil. Because of these results, Rutherford came to the conclusions that the reason for most of the alpha particles going straight through the foil was because that atoms are mostly made of empty space. For the alpha particles that were deflected, he said that this was because of a positive nucleus contained within the atom, and as like charges repel, they were repelled away from the positive gold foil. The few amount of alpha particles that were deflected straight back led Rutherford to believe that the positive charge and mass were contained within the nucleus at the centre of the atom; because of the slim likelihood that this nucleus would collide with the foil, it explained the few particles that this occurred in. These conclusions provided the foundations for the nuclear model: the atom containing mostly empty space, except for a positively charged nucleus, which contained the mass of the atom, surrounded by electrons.