Talk:Potassium-40/Archive 1

Where does it come from ?
Where does the potassium-40 come from ?

Is it a fission decay product ? Does it come from activation of stable atoms by cosmic rays ? Or has all the potassium-40 present now, been in existence since a supernova somewhere long ago ? Eregli bob (talk) 00:42, 7 April 2011 (UTC)

It was produced at the same time as all the other "heavy" elements on the planet - that is in a supernova.

Baska Baska436 (talk) 00:07, 22 July 2011 (UTC)

Not quite. K 39,40, & 41 all come *mostly* from Type II Supernovae but (at least) K-40 also is created via S-process and Neon-burning process nucleosyntheses.Abitslow (talk) 16:30, 15 November 2013 (UTC)

Energy of emitted radiation
The text of the article and many sources found in the net say that the main decay branch yields a 1.460 MeV gamma ray, with error of a few keV at most. However the diagram displayed in the article seems to say that gamma ray has 1.5049 MeV, a difference of 44.9 keV. Is this the energy carried away by the neutrino? Ditto for the secondary branch: sources say 1.33 MeV beta, the diagram says 1.31109 MeV. --Jorge Stolfi (talk) 15:13, 10 June 2011 (UTC) The text refers to the electromagnetic radiations accompanying electron capture as Gamma. This radiation results from the subsequent rearrangement of electrons (by cascade effect) after a K-shell electron has been captured. This would make the radiation x-ray as it is produce by electrical transition outside of the nucleus, rather than gamma as the article states. To be gamma radiation the transition must be nuclear. — Preceding unsigned comment added by 86.15.142.153 (talk) 22:22, 17 January 2015 (UTC)

Electromagnetic radiation accompanying electron capture
The text refers to the electromagnetic radiations accompanying electron capture as Gamma. This radiation results from the subsequent rearrangement of electrons (by cascade effect) after a K-shell electron has been captured. This would make the radiation x-ray as it is produced by electrical transition outside of the nucleus, rather than gamma as the article states. To be gamma radiation the transition must be nuclear. — Preceding unsigned comment added by 86.15.142.153 (talk) 17:53, 18 January 2015 (UTC)


 * I looked at the X-ray and gamma ray articles and it seems that the naming conventions are not that clear cut: “One common alternative is to distinguish X- and gamma radiation on the basis of wavelength.” And “in physics and astronomy, the converse convention (that all gamma rays are considered to be of nuclear origin) is frequently violated.” I added an explanatory note to the article. —Edgar.bonet (talk) 09:46, 19 January 2015 (UTC)

How many types of beta decay?
According to Beta_decay, there are only 2 types of beta decay, but the second paragraph here states that Potassium-40 "undergoes all three types of beta decay." The electron-capture decay mode seems to be conflated with beta decay. Am I missing something? — Preceding unsigned comment added by 98.230.136.131 (talk) 21:54, 2 November 2011 (UTC)
 * It is often conflated, as the basic process (mediated by the weak force) is the same. Double sharp (talk) 04:14, 10 July 2016 (UTC)

That this article implicitly posits that electron capture is a type of beta decay while Beta decay ignores it up front and then leaves the taxonomy vague down below is not satisfactory. A non-specialist is not well-served by this unnecessary obscurity. Lewis Goudy (talk) 01:10, 15 March 2017 (UTC)

0.5 Bq not 5000!
Someone please revise this part

... hence about 0.000117 x 160 = 0.0187 grams of 40K; whose decay produces about 4,900 disintegrations per second (becquerels) continuously throughout the life of the body.[2][3]

The math does not add up at all following the source, which mentions 33 Bq/gram for this isotope. I get a mere 0.5 Bq, given the amount mentioned before (5000 Bq would be very dangerous!)

Also one of the "references" in that sentence is an inconsistent footnote by the author and not actually a reference. --85.84.229.197 (talk) 21:37, 3 July 2014 (UTC)


 * You misinterpreted the source. The numbers given are in Bq per gram of potassium, not per gram of 40K. To get the activity of 40K you have to divide those numbers by the abundance, which is about 117 ppm.


 * As for the reference being a footnote, I fixed the heading. Also, you claim the footnote is “inconsistent”, but I could not find any inconsistency in it. —Edgar.bonet (talk) 08:02, 4 July 2014 (UTC)

The value 4900 is based on 160g K which is incorrect. Composition_of_the_human_body has some problems but tabulates 140g K. Cf. Ref. 11 thereof, corroborated by https://books.google.com/books?id=syjLBAAAQBAJ&pg=PA31#v=onepage&q&f=false, so I revised the article accordingly. Lewis Goudy (talk) 02:10, 15 March 2017 (UTC)

sources?
The statement "It has been proposed that significant core radioactivity (1-2 TW)" in reference to earth's core, is quite curious. Are there any sources for this statement?Wikibearwithme (talk) 18:53, 17 April 2017 (UTC)
 * There is a nice article on the topic.--Stone (talk) 20:32, 17 April 2017 (UTC)