Isotopes of nickel

Notable isotopes

The known isotopes of nickel range in mass number from ⁴⁸Ni to ⁸²Ni, and include:

Nickel-48, discovered in 1999, is the most neutron-poor nickel isotope known. With 28 protons and 20 neutrons ⁴⁸Ni is "doubly magic" (like ²⁰⁸
Pb) and therefore much more stable, with a half-life around 3 milliseconds, than would be expected from its position in the chart of nuclides. It has the highest ratio of protons to neutrons (proton excess) of any known doubly magic nuclide.

Nickel-56, also doubly magic, is produced in large quantities in supernovae. In the last phases of stellar evolution of very large stars, fusion of lighter elements like hydrogen and helium comes to an end. Later in the star's life cycle, elements including magnesium, silicon, and sulfur are fused to form heavier elements. Once the last nuclear fusion reactions cease, the star collapses to produce a supernova. During the supernova, silicon burning produces ⁵⁶Ni. This isotope of nickel is favored because it has an equal number of neutrons and protons, making it readily produced by fusing two ²⁸Si atoms. ⁵⁶Ni is the last element that can be formed in the alpha process. Past ⁵⁶Ni, nuclear reactions are endoergic and energetically unfavorable. ⁵⁶Ni decays to ⁵⁶Co and then ⁵⁶Fe by β+ decay. The radioactive decay of ⁵⁶Ni and ⁵⁶Co supplies much of the energy for the light curves observed for stellar supernovae. The shape of the light curve of these supernovae display characteristic timescales corresponding to the decay of ⁵⁶Ni to ⁵⁶Co and then to ⁵⁶Fe.

Nickel-58 is the most abundant isotope of nickel with a 68.077% natural abundance. It is the only isotope theoretically unstable toward double beta decay.

Nickel-59 is a long-lived cosmogenic radionuclide with a half-life of 81,000 years. ⁵⁹Ni has found many applications in isotope geology. ⁵⁹Ni has been used to date the terrestrial age of meteorites and to determine abundances of extraterrestrial dust in ice and sediment.

Nickel-60 is the daughter product of the extinct radionuclide ⁶⁰
Fe (half-life 2.62 My). Because ⁶⁰Fe has such a long half-life, its persistence in materials in the Solar System at high enough concentrations may have generated observable variations in the isotopic composition of ⁶⁰Ni. Therefore, the abundance of ⁶⁰Ni in extraterrestrial material may provide insight into the origin of the Solar System and its early history/very early history. Unfortunately, nickel isotopes appear to have been heterogeneously distributed in the early Solar System. Therefore, so far, no actual age information has been attained from ⁶⁰Ni excesses. ⁶⁰Ni is also the stable end-product of the decay of ⁶⁰Zn, the last rung of the alpha ladder.

Nickel-61 is the only stable isotope of nickel with a nuclear spin (I = 3/2), which makes it useful for studies by EPR spectroscopy.

Nickel-62 has the highest binding energy per nucleon of any isotope for any element, when including the electron shell in the calculation, though iron-56 has the lower mass-energy per nucleon. Though fusion could form heavier isotopes exothermically - for example, two ⁴⁰Ca atoms could make ⁸⁰Kr (with 4 positron decays) and liberate 77 keV per nucleon - reactions leading to the iron/nickel region are more probable as they release more energy in total.

Nickel-63 has two main uses: detection of explosives traces, and in certain kinds of electronic devices, such as gas discharge tubes used as surge protectors. A surge protector is a device that protects sensitive electronic equipment like computers from sudden changes in the electric current flowing into them. It is also used in electron capture detectors in gas chromatography for the detection mainly of halogens. It is proposed to be used for miniature betavoltaic generators for pacemakers.

Nickel-64 is the heaviest stable isotope of nickel.

Nickel-78 is one of the element's heaviest known isotopes. With 28 protons and 50 neutrons, nickel-78 is doubly magic, resulting in much greater nuclear binding energy and stability despite a lopsided neutron-proton ratio. Its half-life is 122 ± 5.1 milliseconds. Due to its magic neutron number, ⁷⁸Ni is believed to have an important role in supernova nucleosynthesis of elements heavier than iron. ⁷⁸Ni, along with N = 50 isotones ⁷⁹Cu and ⁸⁰Zn, are thought to constitute a waiting point in the r-process, where further neutron capture is delayed by the shell gap and a buildup of isotopes around A = 80 results.