Neutroniluku

Neutroniluku, in Nuclear physics, is the number of neutrons contained in the nucleus of an atom. It is usually denoted by N, while the proton number is Z and the mass number by A. The relation A = Z + N shows that the neutroniluku and the protoniluku together determine the isotope of an element. The neutroniluku distinguishes isotopes of the same element; for example carbon-12 has N = 6, carbon-14 has N = 8, and uranium-235 has N = 143.

The neutroniluku strongly influences nuclear stability and binding energy. Nuclei with too few or too many neutrons relative to protons tend to be radioactive and decay toward more stable configurations. If there is an excess of neutrons (N > Z), beta-minus decay can occur, converting a neutron into a proton. If there is a proton excess (N < Z), beta-plus decay or electron capture can occur, converting a proton into a neutron. The distribution of neutron numbers also reflects shell structure in the nucleus, with special “magic” numbers of neutrons (such as 2, 8, 20, 28, 50, 82, 126) associated with extra stability.

Neutron number is typically inferred from the known mass number and proton number, since A and Z determine N. Isotopes with high neutroniluku are called neutron-rich, while those with relatively low N are neutron-poor. Neutron-rich isotopes play a key role in nuclear structure studies and in astrophysical processes such as the rapid neutron capture process.