Neutron - Wikipedia 000♠−1.04187563(25)×10−3 μB[3] 2999808695726999999♠−1.91304273(45) μN[3] Magnetic polarizability 6996370000000000000♠3.7(20)×10−4 fm3 Spin 1/2 Isospin −1/2 Parity +1 Condensed I(JP) = 1/2(1/2+) <span>The neutron is a subatomic particle, symbol n or n0 , with no net electric charge and a mass slightly larger than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons behave similarly within the nucleus, and each has a mass of approximately one atomic mass unit, they are