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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).
Of the 25 known isotopes of sulfur, four are stable. [1] In order of their abundance, those isotopes are 32 S (94.93%), 34 S (4.29%), 33 S (0.76%), and 36 S (0.02%). [2] The δ 34 S value refers to a measure of the ratio of the two most common stable sulfur isotopes, 34 S: 32 S, as measured in a sample against that same ratio as measured in a known reference standard.
This is an accepted version of this page This is the latest accepted revision, reviewed on 6 January 2025. This article is about the chemical element. For other uses, see Sulfur (disambiguation). Chemical element with atomic number 16 (S) Sulfur, 16 S Sulfur Alternative name Sulphur (pre-1992 British spelling) Allotropes see Allotropes of sulfur Appearance Lemon yellow sintered microcrystals ...
Isotope geochemistry is an aspect of geology based upon the study of natural variations in the relative abundances of isotopes of various elements.Variations in isotopic abundance are measured by isotope-ratio mass spectrometry, and can reveal information about the ages and origins of rock, air or water bodies, or processes of mixing between them.
For other isotopes, the isotopic mass is usually within 0.1 u of the mass number. For example, 35 Cl (17 protons and 18 neutrons) has a mass number of 35 and an isotopic mass of 34.96885. [7] The difference of the actual isotopic mass minus the mass number of an atom is known as the mass excess, [8] which for 35 Cl is –0.03115.
With the discovery of oxygen isotopes in 1929, a situation arose where chemists based their calculations on the average atomic mass (atomic weight) of oxygen whereas physicists used the mass of the predominant isotope of oxygen, oxygen-16. This discrepancy became undesired and a unification between the chemistry and physics was necessary. [13]
Sulfur isotope ratios are almost always expressed as ratios relative to 32 S due to this major relative abundance (95.0%). Sulfur isotope fractionations are usually measured in terms of δ 34 S due to its higher abundance (4.25%) compared to the other stable isotopes of sulfur, though δ 33 S is also sometimes measured.
In the atomic symbol of 32 S, the number 32 refers to the mass of each sulfur atom in daltons, the result of the 16 protons and 16 neutrons of 1 dalton each that make up the sulfur nucleus. The three rare stable isotopes of sulfur are 34 S (4.2% of natural sulfur), 33 S (0.75%), and 36 S (0.015%). [4]