Rutherford's gold foil experiment using alpha particle scattering concluded that atoms consist mostly of empty space with a small, dense, positively charged nucleus at the center. Most alpha particles passed straight through the gold foil, indicating that most of the atom is empty space. However, some alpha particles were deflected at small angles, and a few were even deflected back, showing that the positive charge and most of the atom's mass are concentrated in a tiny nucleus. This experiment disproved the earlier plum pudding model and led to the nuclear model of the atom. The nucleus is very small compared to the overall size of the atom, and electrons orbit this nucleus.