Rutherford’s alpha-particle

Ernest Rutherford’s alpha-particle scattering experiment, conducted in 1909 and published in 1911, was responsible for the discovery of the atomic nucleus [1]. By bombarding a thin gold foil with alpha particles, Rutherford and his colleagues observed that while most particles passed through, some were scattered at large angles or even backwards [3]. This led Rutherford to conclude that the atom's mass and positive charge are concentrated in a tiny, dense central core, which he termed the nucleus [2]. This discovery overturned the previous 'plum pudding' model and established the nuclear model of the atom. While Rutherford later identified the proton in 1919 and his colleague James Chadwick discovered the neutron in 1932, the specific 1911 alpha-scattering experiment is credited with the discovery of the atomic nucleus [4].

Sources

1. [1] https://en.wikipedia.org/wiki/Rutherford_scattering_experiments
2. [3] https://www.osti.gov/opennet/manhattan-project-history/Events/1890s-1939/exploring.htm
3. [2] https://en.wikipedia.org/wiki/Discovery_of_the_neutron
4. [4] https://www.britannica.com/science/Rutherford-model