1. Neutron (discovered by James Chadwick in 1932) is an elementary particle present in the nuclei of all elements except hydrogen.
2. The mass of a neutron is slightly more than that of a proton & is now known to a high degree of accuracy.
It is mn = 1.00866 u = 1.6749×10 –27 kg
3. Neutron has no charge. Being neutral
(a) doesn’t interact with electrons & & doesn’t ionize the gas & hence doesn’t produce any track in the Wilson Cloud chamber.
(b) are not repelled or attracted by the nucleus and the electrons of an atom & consequently can easily penetrate heavy nuclei and induce nuclear reactions.
4. Inside a nucleus, a neutron is stable. But outside a nucleus, it is unstable. A free neutron spontaneously decays into a proton, electron and antineutron (an elementary particle with zero charge and zero rest mass) with a mean life of about 1000 s.