Neutroner

Neutrons (neutroner in some languages) are neutral subatomic particles that reside in atomic nuclei alongside protons. They have a mass of about 1.675×10^-27 kg (roughly 1 atomic mass unit) and a spin of 1/2. Each neutron is made of three quarks (one up and two down) bound by the strong force, with gluons mediating the interaction.

Because they carry no charge, neutrons interact weakly with electromagnetic fields. A free neutron is unstable and beta decays to a proton, an electron, and an electron antineutrino with a mean lifetime of about 14.7 minutes. Neutrons bound in nuclei can be stable for very long times, depending on the isotope.

In nuclei, neutrons contribute to binding energy and determine isotope stability. The neutron-to-proton ratio affects whether a nucleus is stable. The total number of neutrons is N, protons Z, and mass number A = N+Z.

Neutrons interact via the strong nuclear force with other nucleons and via the weak force in decay. They interact weakly with electrons and most nuclei, primarily through scattering and absorption. Their lack of electric charge allows them to penetrate materials, which makes them useful for probing matter.

Neutrons are produced in nuclear reactors, spallation sources, and accelerators. They are used in neutron scattering and imaging to study material structure, in neutron radiography, and in therapies such as boron neutron capture therapy. Moderation—slowing fast neutrons to thermal energies—is common in reactors and experiments.

In astrophysics, neutron-rich matter forms neutron stars, and neutron capture drives nucleosynthesis in stars and supernovae.