The iron peak is a local maximum 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,

nuclear fusion Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles ( neutrons or protons). The difference in mass between the reactants and products is manife ...

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, with the alpha elements being particularly abundant. Some heavier elements are produced by less efficient processes such as the r-process and s-process. 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. 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 In physics and chemistry, a nucleon is either a proton or a neutron, considered in its role as a component of an atomic nucleus. The number of nucleons in a nucleus defines the atom's mass number (nucleon number). Until the 1960s, nucleons were ...

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 Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into a different atomic nucleus, with a mass number that is reduced by four and an at ...

and nuclear fission. is the most thermodynamically favorable in the cores of high-mass stars. Although iron-58 and

nickel-62 Nickel-62 is an isotope of nickel having 28 protons and 34 neutrons. It is a stable isotope, with the highest binding energy per nucleon of any known nuclide (8.7945 MeV). It is often stated that 56Fe is the "most stable nucleus", but only beca ...

have even higher (per nucleon) binding energy, their synthesis cannot be achieved in large quantities, because the required number of

neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...

s is typically not available in the stellar nuclear material, and they cannot be produced in the

alpha process 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, a ...

(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