Neutrons were discovered on February 7, 1932.

The scientific magazine Nature published on February 7, 1932 an article by James Chadwick that would change our conception of matter, entitled Possible Existence of a Neutron. A few months later, on June 1, the article in which the physicist and Nobel laureate finally proved the existence of the neutron was published in the Royal Society.

Chadwick bombarded a thin sheet of beryllium with alpha particles, and the metal emitted very high-energy radiation, similar to gamma rays. Later experiments showed that these rays actually consist of a third type of subatomic particle, which Chadwick called neutrons because they were electrically neutral. With this discovery, for the first time, a complete picture of the atom was offered, something of capital importance for physics and chemistry.