Explanation:
Rutherford proposed a revised model for the atom, called the planetary model. The previous model of the atom was Thomson's Plum Pudding Model which consisted of freely moving positive and negative charges inside the atom.
Rutherford proposed his model after an experiment he conducted called the Gold Foil Experiment. This experiment consisted of a thin gold sheet into which alpha particles were shot upon and they were detected by a sensor. The image attached will give a better explanation of this. In this experiment he shot a beam of alpha particles(helium nucleus) at a thin sheet of gold. Rutherford hypothesised that there should be minimum deflection of the positively charged alpha particles occuring due to the repulsion of the alpha particle with the positive charges in the thin gold sheet. This was not the case.
However what he found was that most of alpha particles went straight through the thin sheet of gold but some were reflected back to him. This surprised him. Hence he proposed that most of the atom must be empty space as most of the alpha particles went straight through the sheet and there must be a heavy nucleus inside the atom causing the alpha particles to bounce back.
