Скачать или смотреть class 9th chemistry Structure of Atom

In 1930, Walther Bothe and Herbert Becker found that if the energetic alpha particles emitted from polonium fell on certain light elements, specifically beryllium, boron or lithium, an unusually penetrating radiation was produced. They observed penetrating radiation was not influenced by an electric field, however, so it was thought to be gamma radiation.

In 1932 Irène Joliot-Curie and Frédéric Joliot showed that if this unknown radiation fell on paraffin wax, it ejected protons of very high energy (5 MeV). A young Italian physicist Ettore Majorana declared that the manner in which the new radiation interacted with protons required a new neutral particle.

In the same year James Chadwick assisted by Norman Feather performed a series of experiments. Chadwick measured the range of these protons, and also measured how the new radiation impacted the atoms of various gases. He found that the new radiation consisted of uncharged particles with about the same mass as the proton. These particles were named neutron. Chadwick won the Nobel Prize in Physics in 1935 for this discovery.