Rutherford's alpha ($\alpha$) particle scattering experiment resulted into the discovery of

In 1911, Ernest Rutherford performed his famous $\alpha$ -particle scattering experiment by bombarding a thin gold foil with high-energy alpha streams.Observing that a tiny fraction of the alpha particles bounced straight back led him to conclude that the positive charge and nearly all the mass of an atom are concentrated in an incredibly small, dense central region. This discovery introduced the atomic nucleus to science.