Up to 1932 it was postulated that an atom is composed of only protons and electrons, and that the mass of an atom is due to the mass of protons present in the nucleus, since the mass of electrons is negligible. Mass of electrons is negligible. Mass of each protons is equal to 1.00376 atomic mass unit (a.m.u).
Rutherford noticed that the atomic masses of different atoms could not be explained if it is supposed that the atom is composed only of protons and electrons and therefore he predicted in 1920 that some kind of neutral particles having mass equal to protons must be present in an atom.
It was in 1932 that Chadwick discovered these neutral particles for which he was awarded the Nobel Prize in Physics in 1936. He obtained these neutral particles by bombarding light nuclei Li and Be with x-particles. He named these particles as neutrons on account of their neutral nature.
Rutherford noticed that the atomic masses of different atoms could not be explained if it is supposed that the atom is composed only of protons and electrons and therefore he predicted in 1920 that some kind of neutral particles having mass equal to protons must be present in an atom.
It was in 1932 that Chadwick discovered these neutral particles for which he was awarded the Nobel Prize in Physics in 1936. He obtained these neutral particles by bombarding light nuclei Li and Be with x-particles. He named these particles as neutrons on account of their neutral nature.
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