Why is it that neutron have no charge?

   The atomic mass is concentrated in the nucleus, the electrons going round it contributing very little to the mass of the nucleus. The positive charge on the nucleus equals the charge on the electron. All nuclei other than hydrogen are made of protons which were brought together against the Columbian force of repulsion at very high temperatures.

 The formation of nuclei in nature suggests the presence of a strong force which is charge independent. The mass of all nuclei is found to be approximately twice the number of charge on the nucleus except in very heavy nuclei like uranium where it is about 2.6 times the charge.

 As the charge on the nucleus is equal to the number of electrons, there should be twice as much matter in the nucleus as is needed to explain the charge. It is possible only if the nucleus is made of particles with no charge but mass nearly equal to that of a proton.

 In 1932, James Chadwick observed that when beryllium was bombarded by alpha particles radiation which were neutral in charge were emitted.

 He repeated the experiment with different materials to establish the fact that the mass of the particles was about 1 mass unit and charge to be neutral. In 1935 Chadwick was given the Nobel Prize in Physics for this great discovery, seeing the missing part of the nucleus!