Neutrons and Protons are the components of the atomic core or nucleus. Both have identical mass (1,67×10-27 kg) but Neutrons are electrically neutral while Protons carry positive charge. In general the numbers of Protons and Neutrons in the nucleus are identical, but not allways. Protons and Neutrons in total detemine the mass of the atom.
Neutrons have been discovered in 1932 by Chadwick.