What is a Neutron

Atoms are the building blocks of all the matters in the universe. ‘Atom’ is a Greek word which means indivisible or uncutable. All atoms are made up of nucleus which is surrounded by electrons. The nucleus of an atom is made up of two sub-atomic particles called proton and neutron. While proton is a positively charges sub particle, neutron has no charge and is neutral. It is represented by n or n0. All the atoms nuclei has got proton and neutron. Number of Proton forms the atomic number of the atom defining the type of element it forms, whereas the mass of the atom is due to both proton as well as neutron. The neutron in the nucleus binds strongly the proton in the nucleus. The protons have positive charge on them hence they repel each other with strong electromagnetic charges which is more than the attraction force between them. The number of neutrons in the nucleus of an atom is called as neutron number and it is the number of this sub atomic particle that determines the isotope of an element. For example, carbons has an atomic number of 12 and thus have 6 proton and 6 neutron in its nucleus, however, the very rare radioactive carbon isotope has has 6 proton and 8 neutrons.


The neutron when in the nucleus of an atom are stable while when in free state they are unstable and undergo decay releasing beta particles in less than 881 sec. The half-life of neutron is 881 sec. Half-life of an object or element is defined as the time in which half of the matter decays. Free neutrons are produced during the process of nuclear fission and nuclear fusion. The sources of neutron are the research reactors and spallation sources which produce free neutrons for use in irradiation and neutron scattering experiments. The free neutrons are sometimes included in the tables of nuclides and considered to have an atomic number zero and mass number 1. It is then called as neutronium.


The neutron was discovered in 1932 and in 1933 it was realized that it may initiate a nuclear chain reaction. Thus, in 1930s neutron was used to produce several nuclear transmutations. In 1938, after the discovery of the process called nuclear fission, it was soon realized that it can be used to produce neutron for the chain reaction. This was proved in the year 1939 and led to the formation of first man made nuclear chain reaction named Chicago Pile-1 and eventually the first nuclear weapon in the year 1945. The advent of neutron is described as one of the path-breaking discovery in the history of mankind.