Neutron

Charge-neutral hadron with a mass of 1.6748 x 10-27 kg, equivalent to 939.573 MeV, and an intrinsic angular momentum, or spin, of ½ (in units of h/2π). The neutron is a nucleon, one of the two basic constituents of all atomic nuclei (apart from 1H, which consists of a single proton). The total number of protons and neutrons in an atomic nucleus defines its mass number, A. Neutrons are stable within the nucleus, but unstable in isolation (t½ = 886±2 s), decay being mediated by a W boson:


Some or all content above used with permission from J. H. Wittke.