Talk:Argon

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Use of the term "preferred isotope"[edit]

The second paragraph ends with, 

...being the preferred argon isotope produced by stellar nucleosynthesis in supernovas.

I am far from an expert in the proper use of terms for this sort of topic, but: It appears to me that the word "preferred" implies some sort of agency, as if the supernova "prefers" to produce one isotope over than another, and that -- in theory (rhetorically speaking) -- the supernova could "change its preferences" and begin producing more of a different isotope instead.

I'm afraid to suggest an alternative wording, since I can't claim the scientific expertise to edit an article with a green "good" evaluation. However, from a lay reader's perspective, this kind of language makes me think of quasi-scientific writing over the centuries. (E.g., "The moon must want to be attracted to the Earth", as part of an early competing theory of gravitation, which I heard discussed on a BBC Radio 4 "In Our Time" podcast years ago, and has stuck with me.)

Best regards, 2018-02-11 Sun 19:11, Obl obl 00:13, 12 February 2018 (UTC) — Preceding unsigned comment added by Obl obl (talk • contribs)

@Obl obl: I think that this sort of use is common mostly because no one writing this sort of thing seriously thinks the supernova has agency, and so that reading just doesn't get consciously considered. For example, when we say that a process favours some product, we're not even considering the interpretation that the process has volition, though we would readily concede the point if pressed. That sort of quasi-scientific reading has just been erased from our minds too well! ^_^ Since this can be clarified without doing violence to the text, I've done so, writing instead that 36Ar is the most easily produced isotope rather than the preferred isotope. Thank you for your suggestion! Double sharp (talk) 04:58, 12 February 2018 (UTC)

Conventional atomic weight[edit]

Please check the current value of the conventional atomic weight of argon: it is either 39.948 (https://www.isotopesmatter.com/applets/IPTEI/IPTEI.html) or 39.95 (https://applets.kcvs.ca/IPTEI/IPTEI.html and https://iupac.org/wp-content/uploads/2015/02/IPTEI_postprint_20190301.pdf, p. 47) – Alexander Lozovsky (talk) 12:48, 8 October 2019 (UTC)

Before "2017", Ar, standard(Ar) was 32.948(1) (Meija "2013", table 1). From this value, the abdrigded value (table 2) is derived, in the argon case incidentally the same: Ar, abridged(Ar) = 32.948(1) (Meija "2013", table 2). This is the value that appears in your first source (with the addition "* proposed"?).
Per "2017" nominally (CIAAW 2017), Ar, standard(Ar) was changed into an interval: [39.792, 39.963]. (This value appears in both of your links). A conventional value for this interval was not published (as the other elements with interval notation have, Meija table 3). The conventional value should be calculated then. I'm not sure, but this might be it:
Step 1: interval into abridged form: round to 5 digits for argon results in [39.792, 39.963] (unchanged, incidentally).
Step 2: from this interval, go to a single conventional value: take mean of the border values:
(39.792 + 39.963)/2 = 39.8775.
Step 3: Round to prevent suggesting overprecision:
Rounded into <= precision than the original value: 39.88.
Conclusion: 39.88 is the "conventional" value to use. The rouding process (setting precision) may be off, I'd like to learn more.
The value 39.95 you mention does not follow from this calculation. Note that this value lies away (at 90%) from the middle of the interval (=at 50%). Is there a background for this? Was the pre-2017 abridged value 39.948 used (Meija "2013", table 2) and rounded into 39.95? -DePiep (talk) 13:30, 8 October 2019 (UTC)
  • Meija, Juris; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
  • "Standard atomic weights of 14 chemical elements revised". CIAAW. 2018-06-05.
  • Ar(E) values used in this wiki: Standard_atomic_weight#List_of_atomic_weights
► As the Updated IUPAC Technical Report of 2019 says, "Some users of atomic-weight data need a value that is not an interval, such as for purposes of trade and commerce. For these users, a conventional atomic-weight value [4] is provided for each of these 13 elements and is shown in white (Figs. 1.1 and 1.2)" (p. 4), where [4] is (see note). Both Fig. 1.1 (p. 3) and Section 4.18 Argon (p. 47) show value 39.95 for argon. As for me, it looks pretty official. Also, Fig. 1.1 shows conventional atomic-weight values for all the thirteen elements in question (i.e. gives the complete list).
Then, you say "Note that this value lies away (at 90%) from the middle of the interval (=at 50%). Is there a background for this?".
As the CIAAW|Argon points out, "While atmospheric argon can serve as an abundant and homogeneous isotopic reference, deviations from the atmospheric isotopic ratios in other argon occurrences limit the precision with which a standard atomic weight can be given for argon. Published data indicate variation of argon atomic weights in normal terrestrial materials between 39.792 and 39.963. The upper bound of this interval is given by the atomic mass of 40Ar, as some samples contain almost pure radiogenic argon-40. The lower bound is derived from analyses of pitchblende (uranium mineral) containing large amounts of nucleogenic 36Ar and 38Ar".
Since most of the atmospheric argon is provided by the decay of potassium-40, it is no surprise that it is almost pure radiogenic argon-40, hence the shift to the upper bound in the conventional atomic-weight value (which indicates that mostly you come across samples rich of argon-40).
  • [4] J.Meija,T.B.Coplen,M.Berglund,W.A.Brand,P.D.Bièvre,M.Gröning,N.E.Holden,J.Irrgeher,R.D.Loss,T.Walczyk, T. Prohaska. Pure Appl. Chem. 88, 265 (2016).
– Alexander Lozovsky (talk) 16:00, 8 October 2019 (UTC)
I agree with Alexander Lozovsky; we should use 39.948 (though marked as proposed), as that is the value IUPAC gives for the conventional atomic weight (marked there as proposed, but very likely for the reasons Alexander Lozovsky states). Double sharp (talk) 16:12, 8 October 2019 (UTC)
 Done Double sharp (talk) 16:18, 8 October 2019 (UTC)
Thanks User:Alexander Lozovsky for the post. As I wrote, " A conventional value for this interval was not published" that is, with the "2017" technical report change (into interval). But now it is, in the Update. As for Double sharps push for 39.948 and not 39.95: I dispute that choice. Its status is "proposed" for a reason. On the other hand, the Update 2019 (2019-03-01) Lozovsky provided, an IUPAC publication, clearly says 39.95. This is the lates publication. -DePiep (talk) 16:35, 8 October 2019 (UTC)
@DePiep: I only had time to look at the first source, so I put 39.948 as it looked familiar (it's the pre-abridged value). Since I see now that 39.95 is the current one and 39.948 is only proposed, I would support 39.95, to be updated to 39.948 when the proposal is accepted. I need to go again now for a moment; you can change it to 39.95 with the other source and without the "proposed" (or I can do it myself later). Double sharp (talk) 16:59, 8 October 2019 (UTC)
► Please also take into account that applets at IsotopesMatter.com and KCVS.ca are of different versions. The former is "Version/Date: 2.0.0, July 17th, 2018" and the latter is "Version/Date: 2.1.0, June 13th, 2019". So it seems like the proposal has already been discussed and the 39.95 value has been supported. – Alexander Lozovsky (talk) 17:35, 8 October 2019 (UTC)
@Alexander Lozovsky and DePiep: I've changed it to 39.95 throughout. Double sharp (talk) 20:27, 8 October 2019 (UTC)
@Double sharp and Alexander Lozovsky: thanks all! Will read the replies later on carefully. The major issue is solved anyway. I planned to refine the sources (into good wiki ref's), and re-read this thread to get it. Lozovsky, your contribution is great, please come back again :-). You have pointed to the weak spot in atomic weights (weak over at IUPAC that is [1]) -DePiep (talk) 20:55, 8 October 2019 (UTC)
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