The nuclear model of the atom, proposed by Ernest Rutherford in 1911, suggests that an atom consists of a dense central nucleus that contains most of its mass and is positively charged, surrounded by a cloud of negatively charged electrons. This model arose from Rutherford’s famous gold foil experiment, where he directed alpha particles at a thin sheet of gold foil.
In this experiment, most alpha particles passed straight through the foil, while a small number were deflected at large angles, with a few even bouncing straight back. This unexpected result could not be explained by the earlier plum pudding model, which suggested that positive charge was spread out throughout the atom. Instead, the observations indicated that the positive charge and mass were concentrated in a small, dense nucleus at the center of the atom.
The nuclear model explains the scattering results as follows: when alpha particles, which are positively charged, approached the nucleus, they experienced a strong electrostatic repulsion due to the concentration of positive charge within the nucleus. If an alpha particle came close enough to the nucleus, the repulsion could be significant enough to cause a deflection or even a backscattering of the particle. The large majority of alpha particles traveled through the foil, indicating that most of the atom is empty space, but the ones that were deflected provided crucial evidence for the existence of a concentrated nucleus.
In summary, the nuclear model of the atom effectively explains the results of alpha particle scattering through the concept of a dense nucleus surrounded by electrons, accounting for both the majority of particles that passed through and the small fraction that were deflected.