Chadwick performed the same experiment of Rutherford but with beryllium/boron sheet few years after Rutherford’s. He found that new particles carrying no charge and mass almost equal to proton were emitted. This neutral particle is known as neutron.
Rutherford suggested an atomic model based upon his scattering experiment and the discovery of neutrons:-
a) An atom has a minute and positively charged body at its centre known as nucleus. According to him, nucleus contains all the protons and neutrons of the atom. As protons and neutrons constitute most of the mass of the atom, most of the mass of the atom resides in nucleus.
b) To balance the positive charge of the protons present inside the nucleus, there are present electrons distributed around the nucleus.
He further explained the reason for electron not falling in to the nucleus in spite of the mutual electrostatic forces of attraction between the electron outside and the protons inside the nucleus. He proposed that the electrons are revolving at such a high velocity that the centrifugal force acting outwards balances the electrostatic forces of attraction acting inwards and due to the same reason, electrons do not fall in to the nucleus.
Though it was a good model but there was a major objection to it which is as follows:-
Niels Bohr was the one who pointed out a major anomaly in Rutherford’s atomic model. He pointed out Rutherford’s atom as unstable based on what J.C. Maxwell had shown a few years back. According to Maxwell, when an electric charge is under acceleration, it looses its energy constantly by emitting radiations. So by what Rutherford proposed about the atomic structure, the electrons revolving around the nucleus should loose energy (as suffer acceleration due to continuous change in direction) and ultimately should fall in to the nucleus but this does not happen.
