Answer: most of the atom\'s mass but very little of its size.
Explanation:
In Rutherford's gold foil experiment. experiment, he took a gold foil and bombarded it with alpha particles (positively charged particles).
Some of the particles deflected their path and a few of them returned straight back. From this he concluded that in an atom, a small positive charge exist in the centre.
He also concluded that an atom consist of a lot of empty space as most of the alpha particles passed without any deflection.
Hence, this experiment concluded that a small positively charged nucleus is present and there is a lot of empty space.