English physicist who worked with Rutherford on the bombardment of elements with alpha particles. In the 1920s, Rutherford and Chadwick attempted to find a uncharged elementary particle, but failed. Then, Chadwick repeated the earlier experiment of Bothe and Frédéric and Iréne Joliot-Curie by exposing beryllium to alpha particles. The Be then gave off radiation which could eject protons from the paraffin.

In 1932, Chadwick showed that a neutral particle beam was the only way to interpret the ejection of protons. This amounted to the discovery of the neutron. For this, he received the 1935 Nobel Prize in physics. With Goldhaber, Chadwick also determined the structure of the deuteron. Furthermore, he showed that the spectrum of beta particles emitted by radioactive elements was continuous, providing the experimental need for neutrinos, and discovered deviation from the r^-2 law for deep Rutherford scattering.

Bothe, Goldhaber, Joliot-Curie (Frederic), Joliot-Curie (Irene), Rutherford