The Geiger-Marsden experiment, also known as the Rutherford gold foil experiment, was conducted by Ernest Marsden and Hans Geiger under the supervision of Ernest Rutherford in 1909. This experiment revolutionized the understanding of atomic structure and led to the development of the nuclear model of the atom.
The experiment involved directing alpha particles (positively charged particles) at a thin gold foil. The alpha particles were emitted by a radioactive source and were expected to pass through the foil with minimal deflection, based on the prevailing model of the atom at the time, which suggested that atoms were composed of diffuse positive charge with embedded negative electrons.
However, contrary to their expectations, Marsden and Geiger observed that while most alpha particles passed through the foil undeflected, some were deflected at large angles, and a few even bounced directly backward. This unexpected pattern of deflection led to the conclusion that the majority of an atom’s mass and positive charge is concentrated in a tiny, dense nucleus, while the electrons orbit the nucleus at a relatively large distance.
