The scattering of alpha particles by a thin sheet of gold foil. This experiment demonstrated that most particles passed through the foil completely undeflected, while a few were deflected at extremely large angles. This demonstrated that atoms consisted of mostly empty space with a very dense core (the nucleus), thus debunking Thomson's Eric Weisstein's World of Biography plum pudding model.
Alpha Particle, Plum Pudding Model, Rutherford's Model
References
Eisberg, R. and Resnick, R. "Rutherford's Model." §4-2 in Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles, 2nd ed. New York: Wiley, pp. 89-95, 1985.
Griffiths, D. J. "The Classical Era (1897-1932)." §1.1 in Introduction to Elementary Particles. New York: Wiley, pp. 11-14, 1987.
