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In physics, natural abundance (NA) refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass (a weighted average, weighted by mole-fraction abundance figures) of these isotopes is the atomic weight listed for the element in the periodic table. The abundance of an isotope varies from ...
Sulfur (16 S) has 23 known isotopes with mass numbers ranging from 27 to 49, four of which are stable: 32 S (95.02%), 33 S (0.75%), 34 S (4.21%), and 36 S (0.02%). The preponderance of sulfur-32 is explained by its production from carbon-12 plus successive fusion capture of five helium-4 nuclei, in the so-called alpha process of exploding type II supernovas (see silicon burning).
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
1 H (atomic mass 1.007 825 031 898 (14) Da) is the most common hydrogen isotope, with an abundance of >99.98%. Its nucleus consists of only a single proton, so it has the formal name protium. The proton has never been observed to decay, so 1 H is considered a stable isotope.
All other isotopes have half-lives shorter than 17.35 ms. Those isotopes with mass below 10 decay into helium (via short-lived isotopes of beryllium for 7 B and 9 B) while those with mass above 11 mostly become carbon. A chart showing the abundances of the naturally occurring isotopes of boron.
Chlorine (17 Cl) has 25 isotopes, ranging from 28 Cl to 52 Cl, and two isomers, 34m Cl and 38m Cl. There are two stable isotopes, 35 Cl (75.8%) and 37 Cl (24.2%), giving chlorine a standard atomic weight of 35.45. The longest-lived radioactive isotope is 36 Cl, which has a half-life of 301,000 years. All other isotopes have half-lives under 1 ...
The relative abundances of the four stable isotopes are approximately 1.5%, 24%, 22%, and 52.5%, combining to give a standard atomic weight (abundance-weighted average of the stable isotopes) of 207.2(1). Lead is the element with the heaviest stable isotope, 208 Pb.
Rubidium (37 Rb) has 36 isotopes, with naturally occurring rubidium being composed of just two isotopes; 85 Rb (72.2%) and the radioactive 87 Rb (27.8%). 87 Rb has a half-life of 4.92 × 10 10 years. It readily substitutes for potassium in minerals, and is therefore fairly widespread.