neutronens

Neutrons are subatomic particles with no electric charge and a mass slightly larger than that of a proton. Each neutron has a mass of about 1.675 × 10^-27 kilograms and a spin of 1/2, classifying it as a fermion. They reside in atomic nuclei together with protons and, through the strong nuclear force, contribute to the binding energy that holds nuclei together. Because neutrons are neutral, they can penetrate matter more readily than charged particles and thus play a central role in nuclear physics and applications.

Neutrons were identified as a distinct particle by James Chadwick in 1932, following experiments that showed that a neutral, high-energy radiation could dislodge protons from light elements when bombarded with alpha particles. This established the neutron as a separate constituent of the atomic nucleus.

Free neutrons are unstable and decay via beta decay into a proton, an electron, and an antineutrino with a mean lifetime of about 880 seconds (roughly 15 minutes). In bound nuclei, neutrons contribute to stability, with the number of neutrons relative to protons determining the nuclide's stability.

Neutrons are produced in nuclear reactors, spallation sources, and cosmic-ray interactions. They are categorized by energy: thermal, epithermal, fast. In research and industry, they are used for neutron scattering and diffraction to probe material structures, neutron activation analysis, and, in some cases, medical therapies. Moderating materials slow fast neutrons to thermal energies to enhance certain interactions. Safety considerations include shielding to limit exposure from secondary radiation and activation of surrounding materials.