What is a neutron? Definition:

On neutron (n) is an electrically neutral charged subatomic particle. The concept of the neutron derives from the Latin word neutra / neuterum and means 'neither', which of course means the electric charge that is neither positive nor negative. Neutrons together with protons form the atomic nucleus of an atom. Therefore, neutrons are also among the nucleons (Latin nucleus = core), ie those particles that form the nucleus.
With a mass of 1.008u, a neutron is about the same size as a proton and 2000x larger than an electron. The corresponding antiparticle to the neutron is the antineutron. Neutrons outside an atomic nucleus are called free neutrons. Free neutrons are produced e.g. in nuclear reactions or radioactive decay.
Neutrons related to isotopes have further relevance. Atoms with the same atomic number (number of protons) but different numbers of neutrons are called isotopes. A simple example is the three isotopes of hydrogen:
Hydrogen (1 proton, 0 neutrons), deuterium (1 proton, 1 neutron) and tritium (1 proton, 2 neutrons).
Attention: The corresponding isotope series are always the same element! Despite the different mass number, the above isotopes belong to the chemical element hydrogen. Ergo determines the number of protons the chemical element of the atom and the number of neutrons the corresponding isotope.
Interesting: Today, neutron spectroscopy is one of the most central methods in nuclear physics and solid-state physics. Increasingly, this is also important in the field of biology and chemistry. Neverthe- less, neutrons can also be the source of nuclear explosions (super-GAU).