Based on the gold foil experiment and the resulting model of the atom, one of the main conclusions is that most of an atom's volume is actually empty space. In this experiment, a beam of alpha particles (helium nuclei) was fired at a thin sheet of gold foil. Most of the alpha particles passed through the gold foil without any deflection, but a small number of them were deflected at large angles. This indicated that the positive charge and most of the mass of an atom are concentrated in a very small, dense nucleus, while the electrons occupy a much larger volume around the nucleus. This model of the atom is often referred to as the "nuclear atom" or "Rutherford model" after the physicist Ernest Rutherford, who conducted the gold foil experiment.