Neutron was discovered by Chadwick.
To overcome the failure of proton electron hypothesis, Rutherford, in 1920, proposed the existence of neutral particle made from close combination of proton and electron. He named it neutron.
In 1932, Lord Chadwick proved the existence of neutron by bombarding lighter elements (boron and beryllium) with alpha particles which resulted in the emission of highly penetrating neutral radiation.