Final answer:
Ernest Rutherford's gold-foil experiment disproved the plum pudding model by showing that atoms have a small, dense, positively-charged nucleus, with electrons orbiting in the surrounding empty space.
Step-by-step explanation:
Ernest Rutherford conducted the gold-foil experiment in 1911, which was pivotal in understanding the structure of the atom. Rutherford bombarded thin gold foil with alpha particles and expected them to pass through without much deflection, as per the then-accepted plum pudding model of the atom.
However, he observed that while most alpha particles passed through, a small number were deflected at large angles. From this, he concluded that the atom must have a very small, dense, positively-charged nucleus at its center, with the electrons orbiting this nucleus in a large volume of mostly empty space, akin to a miniature solar system.
These observations contradicted the plum pudding model and led to the concept of the nucleus being the core of the atom, containing most of its mass and positively charged. The deflection of alpha particles at large angles indicated the substantial mass and density of this central nucleus. This experiment was foundational in the development of the nuclear model of the atom.