The branch of chemistry which deals with the study of nucleus of an atom is known as nuclear chemistry. There are two sub-atomic particles present in the nucleus of an atom. The positive charge on the nucleus is because of the positive charge of proton. Protons and neutrons are involved in nuclear chemistry. Neutrons play an important role in all the nuclear reactions which are taken place in a nucleus of an atom. For example, during nuclear fission reaction, neutron breaks a heavy unstable nucleus into a product of nuclei, a product of neutrons and a large amount of energy. An other important nuclear reaction is nuclear fusion reaction. During nuclear fusion reaction, two small unstable nuclei are combined to form a heavy and stable nucleus with a release of a large amount of energy.