Which physicist discovered the neutron in 1932?

James Chadwick discovered the neutron in 1932.

Chadwick made the discovery at the Cavendish Laboratory in Cambridge, where he investigated radiation produced when alpha particles struck beryllium. The radiation could eject protons from substances such as paraffin, but its behavior could not be explained adequately by ordinary gamma rays.

Chadwick concluded that the radiation consisted of neutral particles with a mass close to that of the proton. He called these particles neutrons and published his result in the journal Nature in February 1932. The discovery clarified the structure of the atomic nucleus and explained why atomic mass could exceed the number of protons.

The neutron quickly became central to nuclear physics. It helped researchers understand isotopes and later made nuclear fission possible. Chadwick received the Nobel Prize in Physics in 1935 for the discovery of the neutron, while Ernest Rutherford had earlier proposed a neutral nuclear particle as a possibility.