Final answer:
Ernest Rutherford performed the gold foil experiment in 1911, which revealed that atoms are mostly empty space with a small, dense nucleus containing all of the positive charge and most of the mass. This discovery was pivotal in the development of the modern atomic model.
Step-by-step explanation:
The scientist who carried out the gold foil experiment demonstrating that most of an atom is empty space was the British physicist Ernest Rutherford. In 1911, Rutherford, along with his coworkers Hans Geiger and Ernest Marsden, initiated a series of experiments where they bombarded very thin sheets of gold foil with fast moving alpha particles. These alpha particles are helium nuclei, meaning they are positively charged and relatively massive.
Rutherford's experiment showed that while most alpha particles passed straight through the foil, a small fraction were deflected at large angles, and about 1 in 8,000 actually rebounded. This led Rutherford to reason that most of the atom was indeed empty space. The few deflected alpha particles indicated the presence of a tiny, dense region in the atom, which Rutherford termed the nucleus. This nucleus, he concluded, contained all the positive charge and most of the mass of the atom.
The experiment not only revealed that atoms are mostly empty space but also led to the proposal of a new atomic model with a central nucleus, overthrowing the then-accepted plum pudding model. Rutherford's finding was a pivotal moment in the field of physics and chemistry, influencing our understanding of atomic structure.