What was Rutherford's conclusion from the alpha particle experiment?

Rutherford concluded that atoms have a small, dense, positively charged nucleus, with electrons orbiting around it.

Ernest Rutherford's alpha particle scattering experiment, also known as the gold foil experiment, led to a significant breakthrough in our understanding of atomic structure. Before this experiment, the widely accepted model was J.J. Thomson's 'plum pudding' model, which suggested that atoms were a uniform sphere of positive charge with negatively charged electrons embedded within.

Rutherford's experiment involved firing alpha particles (which are positively charged) at a thin sheet of gold foil. According to the 'plum pudding' model, the alpha particles should have passed straight through the foil with minimal deflection. However, Rutherford observed that while most alpha particles did pass straight through, some were deflected at large angles, and a few even bounced back.

This observation led Rutherford to conclude that the positive charge and most of the mass of an atom must be concentrated in a very small area, which he called the nucleus. The fact that most alpha particles passed straight through the foil suggested that the rest of the atom was mostly empty space, with electrons orbiting the nucleus at a distance.

This conclusion was a significant departure from the 'plum pudding' model and marked the birth of the nuclear model of the atom. Rutherford's model was later refined by Niels Bohr, who proposed specific energy levels for the orbiting electrons, but the concept of a small, dense, positively charged nucleus remains a fundamental principle of atomic structure.