The neutron is a subatomic particle with neutral charge and a mass slightly greater than that of the proton. Protons and neutrons constitute the nuclei of atoms. Protons and neutrons behave similarly within the nucleus. Each has a mass of approximately one atomic mass unit. They are both referred to as nucleons. Their properties and interactions are described by nuclear physics.
The chemical properties of an atom are mostly determined by the configurations of electrons that orbit the heavy atomic nucleus. The electron configuration is determined by the charge of the nucleus. This is set by the number of protons or the atomic number. Neutrons do not affect the electron configuration. But the sum of the atomic number and the number of neutrons or neutron number is the mass of the atomic nucleus.
Atoms of a chemical element that differs only in neutron numbers are known as isotopes. Some elements occur in nature with only one stable isotope. Some have many.
The properties of the atomic nucleus are dependent both on atomic and neutron numbers.
The neutron is also essential to the production of nuclear power.
The neutron was discovered by James Chadwick in 1932.