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Potassium-40 (40 K) is a radioactive isotope of potassium which has a long half-life of 1.25 billion years. It makes up about 0.012% (120 ppm ) of the total amount of potassium found in nature. Potassium-40 undergoes three types of radioactive decay .
The δ values and absolute isotope ratios of common reference materials are summarized in Table 1 and described in more detail below. Alternative values for the absolute isotopic ratios of reference materials, differing only modestly from those in Table 1, are presented in Table 2.5 of Sharp (2007) [1] (a text freely available online), as well as Table 1 of the 1993 IAEA report on isotopic ...
The template provides a standardised table header for a List of isotopes, as is used in each of the 118 Isotopes of <element> articles. Parameters allow for adjustment of the table header structure, references and table footnotes. This header does not change existing rows: values, isotope-specific footnotes, structure, nor split decay routes ...
19 K) has 25 known isotopes from 34 K to 57 K as well as 31 K, as well as an unconfirmed report of 59 K. [3] Three of those isotopes occur naturally: the two stable forms 39 K (93.3%) and 41 K (6.7%), and a very long-lived radioisotope 40 K (0.012%) Naturally occurring radioactive 40 K decays with a half-life of 1.248×10 9 years. 89% of those ...
Archaeological materials, such as bone, organic residues, hair, or sea shells, can serve as substrates for isotopic analysis. Carbon, nitrogen and zinc isotope ratios are used to investigate the diets of past people; these isotopic systems can be used with others, such as strontium or oxygen, to answer questions about population movements and cultural interactions, such as trade.
t 1/2 is the half-life of 40 K; K f is the amount of 40 K remaining in the sample; Ar f is the amount of 40 Ar found in the sample. The scale factor 0.109 corrects for the unmeasured fraction of 40 K which decayed into 40 Ca; the sum of the measured 40 K and the scaled amount of 40 Ar gives the amount of 40 K which was present at the beginning ...
For instance, on average each gram of potassium contains 117 micrograms of 40 K (all other naturally occurring isotopes are stable) that has a / of 1.277 × 10 9 years = 4.030 × 10 16 s, [4] and has an atomic mass of 39.964 g/mol, [5] so the amount of radioactivity associated with a gram of potassium is 30 Bq.
Sulfur isotope evidence has also been used to corroborate the timing of the Great Oxidation Event, during which the Earth's atmosphere experienced a measurable rise in oxygen (to about 9% of modern values [46]) for the first time about 2.3–2.4 billion years ago. Mass-independent sulfur isotope fractionations are found to be widespread in the ...