Discovery of Neutron:
Rutherford, in 1920, predicted about neutron but it was discovered by James Chadwick in 1932. He performed an experiment.
How the neutron was discovered?
James Chadwick bombarded beryllium with α-particles and found that highly penetrating radiations were emitted from beryllium, which in turn have knocked out protons from paraffin target. By little thinking it was concluded that these rays emitted from beryllium could neither be – ve rays nor + rays, rather they are neutral particles having mass closer to protons. These neutral particles were given the name as neutrons.