The iron peak is a

local maximum In mathematical analysis, the maxima and minima (the respective plurals of maximum and minimum) of a function, known collectively as extrema (the plural of extremum), are the largest and smallest value of the function, either within a given ran ...

in the vicinity of Fe ( Cr, Mn, Fe, Co and Ni) on the graph of the abundances of the chemical elements. For elements lighter than iron on the

periodic table The periodic table, also known as the periodic table of the (chemical) elements, is a rows and columns arrangement of the chemical elements. It is widely used in chemistry, physics, and other sciences, and is generally seen as an icon of ch ...

, nuclear fusion releases energy. For iron, and for all of the heavier elements, nuclear fusion consumes energy. Chemical elements up to the iron peak are produced in ordinary

stellar nucleosynthesis Stellar nucleosynthesis is the creation (nucleosynthesis) 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 ...

, with the

alpha element The alpha process, also known as the alpha ladder, is one of two classes of nuclear fusion reactions by which stars convert helium into heavier elements, the other being the triple-alpha process. The triple-alpha process consumes only helium, an ...

s being particularly abundant. Some heavier elements are produced by less efficient processes such as the

r-process In nuclear astrophysics, the rapid neutron-capture process, also known as the ''r''-process, is a set of nuclear reactions that is responsible for the creation of approximately half of the atomic nuclei heavier than iron, the "heavy elements", ...

and

s-process The slow neutron-capture process, or ''s''-process, is a series of reactions in nuclear astrophysics that occur in stars, particularly asymptotic giant branch stars. The ''s''-process is responsible for the creation (nucleosynthesis) of approximat ...

. Elements with atomic numbers close to iron are produced in large quantities in supernova due to explosive oxygen and silicon fusion, followed by radioactive decay of nuclei such as

Nickel-56 Naturally occurring nickel (28Ni) is composed of five stable isotopes; , , , and , with being the most abundant (68.077% natural abundance). 26 radioisotopes have been characterised with the most stable being with a half-life of 76,000 years, ...

. On average, heavier elements are less abundant in the universe, but some of those near iron are comparatively more abundant than would be expected from this trend. SolarSystemAbundances

Binding energy

A graph of the nuclear binding energy per nucleon for all the elements shows a sharp increase to a peak near nickel and then a slow decrease to heavier elements. Increasing values of binding energy represent energy ''released'' when a collection of nuclei is rearranged into another collection for which the sum of nuclear binding energies is higher. Light elements such as hydrogen release large amounts of energy (a big increase in binding energy) when combined to form heavier nuclei. Conversely, heavy elements such as uranium release energy when converted to lighter nuclei through alpha decay and

nuclear fission Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radio ...

. is the most thermodynamically favorable in the cores of high-mass

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

s. Although

iron-58 Naturally occurring iron (26Fe) consists of four stable isotopes: 5.845% of 54Fe (possibly radioactive with a half-life over years), 91.754% of 56Fe, 2.119% of 57Fe and 0.286% of 58Fe. There are 24 known radioactive isotopes, the most stable of w ...

and nickel-62 have even higher (per nucleon) binding energy, their

synthesis Synthesis or synthesize may refer to: Science Chemistry and biochemistry *Chemical synthesis, the execution of chemical reactions to form a more complex molecule from chemical precursors ** Organic synthesis, the chemical synthesis of organ ...

cannot be achieved in large quantities, because the required number of neutrons is typically not available in the stellar nuclear material, and they cannot be produced in the alpha process (their mass numbers are not multiples of 4).

References

{{reflist, refs= {{cite book , title=Progress in Understanding Iron Peak Elements in Young Supernova Remnants , url=https://books.google.com/books?id=6fHGwQEACAAJ , year=2013 , publisher=Los Alamos National Laboratory , author1=Erikson, K.A. , author2=Hughes, J. , author3=Fontes, C.J. , author4=Colgan, J.P. Astrophysics

Binding energy

See also

References