nêutrons

Nêutrons are subatomic particles found in the nucleus of every atom except ordinary hydrogen. They have no electric charge, a rest mass of approximately 1.67492749804 × 10^-27 kilograms, and a spin of 1/2. Nêutrons are classified as baryons and are composed of three quarks: two down quarks and one up quark. They play a crucial role in nuclear reactions and the stability of atomic nuclei.

Nêutrons are unstable and can decay into a proton, an electron, and an antineutrino, a process known as beta decay. This decay has a half-life of about 10 minutes. Free neutrons, those not bound in an atomic nucleus, are rare due to their instability and the fact that they are repelled by the electric charge of other neutrons. They are typically produced in nuclear reactions, such as those induced by cosmic rays or in particle accelerators.

In nuclear fission, nêutrons are released, which can then induce further fission in nearby nuclei, leading to a chain reaction. This principle is exploited in nuclear power reactors and nuclear weapons. Nêutrons are also used in neutron activation analysis, a technique for determining the composition of materials.

The study of nêutrons and their interactions is a active area of research in nuclear physics and particle physics. Neutron stars, remnants of massive stars that have undergone supernova explosions, are composed almost entirely of neutrons, making them the most dense form of matter known.