An alpha nuclide is a

nuclide Nuclides (or nucleides, from nucleus, also known as nuclear species) are a class of atoms characterized by their number of protons, ''Z'', their number of neutrons, ''N'', and their nuclear energy state. The word ''nuclide'' was coined by the A ...

that consists of an integer number of

alpha particle Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay but may also be produce ...

s. Alpha nuclides have equal, even numbers of

proton A proton is a stable subatomic particle, symbol , Hydron (chemistry), H+, or 1H+ with a positive electric charge of +1 ''e'' (elementary charge). Its mass is slightly less than the mass of a neutron and approximately times the mass of an e ...

s and

neutron The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The Discovery of the neutron, neutron was discovered by James Chadwick in 1932, leading to the discovery of nucle ...

s; they are important in

stellar nucleosynthesis In astrophysics, stellar nucleosynthesis is the creation of chemical elements by nuclear fusion reactions within stars. Stellar nucleosynthesis has occurred since the original creation of hydrogen, helium and lithium during the Big Bang. As a ...

since the energetic environment within stars is amenable to fusion of alpha particles into heavier nuclei. Stable alpha nuclides, and stable decay products of radioactive alpha nuclides, are some of the most common

metals A metal () is a material that, when polished or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. These properties are all associated with having electrons available at the Fermi level, as against no ...

in the universe. Alpha nuclide is also short for '' alpha-emitting nuclide'', referring to those radioactive isotopes that undergo

alpha decay Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus). The parent nucleus transforms or "decays" into a daughter product, with a mass number that is reduced by four and an a ...

and thereby emit alpha particles.

List of alpha nuclides

The entries for ³⁶Ar and ⁴⁰Ca are theoretical: they would release energy on decay, but the process has never been observed, and the half-lives are probably extremely long. Likewise, the chains for masses 64, 84, 92, and 96 theoretically can continue one more step by double electron capture (to ⁶⁴Ni, ⁸⁴Kr, ⁹²Zr, and ⁹⁶Mo respectively), but this has never been observed. , the heaviest known alpha nuclide is xenon-108.

References

{{reflist Nuclear physics