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Isotope half-lives. The darker more stable isotope region departs from the line of protons (Z) = neutrons (N), as the element number Z becomes larger. Isotopes are nuclides with the same number of protons but differing numbers of neutrons; that is, they have the same atomic number and are therefore the same chemical element. Isotopes neighbor ...
A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [ 1 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...
a + b ↔ R → c in the centre of mass frame , where a and b are the initial species about to collide, c is the final species, and R is the resonant state . Physical situation
Part of the Chart of Nuclides showing some stable or nearly-stable s-, r-, and p-nuclei. The classical, ground-breaking works of Burbidge, Burbidge, Fowler and Hoyle (1957) [1] and of A. G. W. Cameron (1957) [2] showed how the majority of naturally occurring nuclides beyond the element iron can be made in two kinds of neutron capture processes, the s- and the r-process.
The term p-process (p for proton) is used in two ways in the scientific literature concerning the astrophysical origin of the elements (nucleosynthesis).Originally it referred to a proton capture process which was proposed to be the source of certain, naturally occurring, neutron-deficient isotopes of the elements from selenium to mercury.
Most stable nuclides have roughly equal numbers of protons and neutrons, so the line for which Z = N forms a rough initial line defining stable nuclides. The greater the number of protons, the more neutrons are required to stabilize a nuclide; nuclides with larger values for Z require an even larger number of neutrons, N > Z, to be stable. The ...
Conversely, of the 251 known stable nuclides, only five have both an odd number of protons and odd number of neutrons: hydrogen-2 , lithium-6, boron-10, nitrogen-14, and tantalum-180m. Also, only four naturally occurring, radioactive odd–odd nuclides have a half-life >10 9 years: potassium-40, vanadium-50, lanthanum-138, and lutetium-176.
Nitrogen-14 is one of the very few stable nuclides with both an odd number of protons and of neutrons (seven each) and is the only one to make up a majority of its element. Each proton or neutron contributes a nuclear spin of plus or minus spin 1/2 , giving the nucleus a total magnetic spin of one.