jan 1, 1932 - Chadwick Discovery of the Neutron

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Following Bothe & Becker and Curie & Juliot experiments, Chadwick suggested that this radiation consisted of Rutherford neutrons.
The emitted radiation suffered no deflection in magnetic and electric fields, so it could not be a charged particle, but it seemed to have too high of an energy content to be radiation. Chadwick then applied laws of conservation of momentum and energy to show that the particles emitted from beryllium bombarded by alpha particles were uncharged particles (neutron) with approximately the same mass as a proton.

The nucleus is thus consisted of protons and neutrons, completing the picture of subatomic particles that make up an atom.

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