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Superheavy elements, also known as transactinide elements, transactinides, or super-heavy elements, or superheavies for short, are the chemical elements with atomic number greater than 104. [1] The superheavy elements are those beyond the actinides in the periodic table; the last actinide is lawrencium (atomic number 103).
Supernova nucleosynthesis is the nucleosynthesis of chemical elements in supernova explosions.. In sufficiently massive stars, the nucleosynthesis by fusion of lighter elements into heavier ones occurs during sequential hydrostatic burning processes called helium burning, carbon burning, oxygen burning, and silicon burning, in which the byproducts of one nuclear fuel become, after ...
Synthesis of these elements occurred through nuclear reactions involving the strong and weak interactions among nuclei, and called nuclear fusion (including both rapid and slow multiple neutron capture), and include also nuclear fission and radioactive decays such as beta decay. The stability of atomic nuclei of different sizes and composition ...
The process of slow neutron capture used to produce nuclides as heavy as 257 Fm is blocked by short-lived isotopes of fermium that undergo spontaneous fission (for example, 258 Fm has a half-life of 370 μs); this is known as the "fermium gap" and prevents the synthesis of heavier elements in such a reaction.
The need for a physical description was already inspired by the relative abundances of the chemical elements in the solar system. Those abundances, when plotted on a graph as a function of the atomic number of the element, have a jagged sawtooth shape that varies by factors of tens of millions (see history of nucleosynthesis theory). [4]
The stable alpha elements are: C, O, Ne, Mg, Si, and S. The elements Ar and Ca are "observationally stable". They are synthesized by alpha capture prior to the silicon fusing stage, that leads to Type II supernovae. Si and Ca are purely alpha process elements. Mg can be separately consumed by proton capture reactions.
Abundance peaks for the r-process occur near mass numbers A = 82 (elements Se, Br, and Kr), A = 130 (elements Te, I, and Xe) and A = 196 (elements Os, Ir, and Pt). The r-process entails a succession of rapid neutron captures (hence the name) by one or more heavy seed nuclei, typically beginning with nuclei in the abundance peak centered on 56 Fe.
A version of the periodic table indicating the origins – including big bang nucleosynthesis – of the elements. All elements above 103 are also man-made and are not included. Big Bang nucleosynthesis produced very few nuclei of elements heavier than lithium due to a bottleneck: the absence of a stable nucleus with 8 or 5 nucleons. This ...