What Is the Alpha Scattering Experiment?

Rutherford's alpha scattering experiment is used to demonstrate the structure of atoms. Beams of alpha particles, nuclei of helium atoms, are used to irradiate a gold foil. Rutherford observed a few alpha particles going straight through, a few small deflections, a few large deflections and a few particles scattered back, which indicates that an atom has an intensely positively charged nucleus at its center.

The alpha particles are produced by radioactive nuclides and are made to hit a gold foil a few atoms deep at a fixed angle in a vacuum. A zinc-sulfide-coated microscope lens attached to a turntable detects the deflected alpha particles at various angles. The lens at zero angle detects a higher number of scintillations per minute, while it detects lower rates at larger angles.

The results of Rutherford's experiments were mathematically evaluated, and the conclusion is that the particles that went straight through indicate the presence of an empty space in an atom. Particles that were less deflected were far away from the nucleus, and those that were more deflected were nearer to the nucleus. The particles that hit the positively charged nucleus were scattered back. Rutherford's new atomic model was accepted over the plum pudding model.