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Most of the isotopes with atomic mass numbers below 14 decay to isotopes of carbon, while most of the isotopes with masses above 15 decay to isotopes of oxygen. The shortest-lived known isotope is nitrogen-10, with a half-life of 143(36) yoctoseconds, though the half-life of nitrogen-9 has not been measured exactly.
Isotopes with equal numbers of protons and neutrons [boxes] are particularly abundant. The elemental basis of the Oddo–Harkins has direct roots in the isotopic compositions of the elements. [ 7 ] While even-atomic-numbered elements are more abundant than odd, the spirit of Oddo–Harkins rule extends to the most abundant isotopes as well.
There are 36 other unstable isotopes recognized, the longest-lived of which are 183 Re with a half-life of 70 days, 184 Re with a half-life of 38 days, 186 Re with a half-life of 3.7186 days, 182 Re with a half-life of 64.0 hours, and 189 Re with a half-life of 24.3 hours.
(The more massive 209 Bi, long considered to be stable, actually has a half-life of 2.01×10 19 years.) 208 Pb is also a doubly magic isotope, as it has 82 protons and 126 neutrons. [6] It is the heaviest doubly magic nuclide known. A total of 43 lead isotopes are now known, including very unstable synthetic species.
All isotopes of a given element have the same number of protons in each atom. The term isotope is formed from the Greek roots isos (ἴσος "equal") and topos (τόπος "place"), meaning "the same place"; thus, the meaning behind the name is that different isotopes of a single element occupy the same position on the periodic table.
Carbon (6 C) has 14 known isotopes, from 8 C to 20 C as well as 22 C, of which 12 C and 13 C are stable.The longest-lived radioisotope is 14 C, with a half-life of 5.70(3) × 10 3 years. . This is also the only carbon radioisotope found in nature, as trace quantities are formed cosmogenically by the reactio
A precise measurement of the neutron-rich 40 Mg in 2019 showed the unexpected difference in its nuclear structure, compared to the lighter neighboring isotopes. [4] [5] The abundances of the naturally occurring isotopes of magnesium.
Arsenic (33 As) has 32 known isotopes and at least 10 isomers. Only one of these isotopes, 75 As, is stable; as such, it is considered a monoisotopic element. The longest-lived radioisotope is 73 As with a half-life of 80 days.