22Ne

22Ne is the stable isotope of neon with mass number 22. It contains 10 protons and 12 neutrons (Z = 10, N = 12). In natural neon, 22Ne accounts for about 9% of the atoms, with the remaining isotopes being 20Ne and 21Ne. The standard atomic mass of 22Ne is 21.991385 u. The ground-state spin and parity of 22Ne is 0+.

Nuclear properties of 22Ne include its stability and its role in stellar nucleosynthesis. As a stable isotope, 22Ne does not undergo radioactive decay under ordinary conditions. It is one of the three naturally occurring neon isotopes and serves as a key product of helium burning in stars. In particular, during helium burning, 14N left from earlier CNO processing is converted through a series of captures and decays to 22Ne.

Astrophysical significance of 22Ne is substantial because it serves as a neutron source in stars. At the temperatures characteristic of helium-burning shells, the reaction 22Ne(α,n)25Mg releases free neutrons, enabling slow neutron capture (the s-process) that builds heavier elements. This neutron production contributes to the chemical evolution of galaxies in both massive stars and asymptotic giant branch stars, and its efficiency depends on the 22Ne abundance established during prior stellar burning.

Occurrence and measurement context include its presence in natural neon gas and in cosmochemical samples. The isotopic composition of neon, including 22Ne, is measured by mass spectrometry in laboratories studying planetary atmospheres, meteorites, and stellar materials. Consequently, 22Ne provides insights into stellar nucleosynthesis, neutron-capture nucleosynthesis, and the history of matter in the solar system.