Why does rutherford's gold-foil experiment conclude that the atom is mostly empty space with a small massive positively charged center?

Answer 1

because few particles bounced back

Answer 2

In Rutherford's gold-foil experiment, when alpha particles were shot at gold foil, most passed straight through, but some were deflected at large angles. This led Rutherford to conclude that the atom is mostly empty space, with a small, dense, positively charged nucleus at the center that caused the deflections. The majority of the atom's volume is made up of this empty space, with the nucleus containing most of the atom's mass.