The third particle that builds matter around us, the neutron, was discovered in 1932 by James Chadwick. (The two first were the electron and the proton.) The neutron was produced in a nuclear reaction similar to the one used by Rutherford when discovering the proton. Chadwick managed to show that the neutral particle produced had approximately the same mass as the proton. The only difference was the electric charge.



The produced neutral particle was not directly detectable. It was identified by Chadwick by studying the protons the neutrons collided with. He concluded that the protons must have been hit by a particle with approximately the same mass as the proton.

[home]    [quarks]     [leptons]    [forces]    [inside matter]