Talk:Standard atomic weight

The awful problem that chemists use "standard atomic weight" yet refer to it as "atomic weight."

It isn't a lot of help when the usual term for a thing is wrong by reason of slang. What is seen in interval notation on periodic tables is the STANDARD atomic weight. That is the value of atomic weight you expect from many samples on Earth, and hence the interval! The atomic weight of a SINGLE sample in a lab can be determined far more accurately with a mass spectrograph, even though usually more than one isotope is being evaluated, and their weighted sum used. That atomic weight can differentiate between samples, using stable isotope ratios. For example, it is differences in atomic weights of carbon from natural testosterone vs. artificial testosterone (which has a carbon atomic weight that looks like a plant) that allows doping commissions to tell if testosterone is taken artificially. Yet all these values are within the "standard atomic weight" for carbon seen on the average periodic table. That is why the two terms are different.

The term "relative atomic mass" is the same as "atomic weight". It is NOT the same as "standard atomic weight." That latter term would need to be "standard relative atomic mass" which is so long it is rarely seen. This is one reason that "atomic weight" continues to hang on. SBHarris 03:30, 7 September 2017 (UTC)

"This range is the cause of the interval notation in some standard atomic weight values": not exactly so. in determining s.a.w, there is a difference between source and sample. Only when values vary between sources, an interval maight be given. Otherwise (no systematic diff between sources), a single value &with uncertainty is given. -DePiep (talk) 15:31, 7 September 2017 (UTC)

Changes published in 2018

Changes to the standard atomic weights of 14 chemical elements have been recommended recently ([1]), this should be incorporated into the article and values be updated accordingly. Szaszicska (talk) 21:26, 7 October 2018 (UTC)

Yes. Surprisingly, the "2017" changes were announced in June 2018. -DePiep (talk) 21:33, 7 October 2018 (UTC)

 Done. See {{Infobox element/symbol-to-saw/standard}} + its documentation. - DePiep (talk) 21:54, 7 October 2018 (UTC)

Conventional value for argon not published yet. Former abridged value looks suspicious. The 13 other changed values appear to be in same abridged bracket; waiting for publication. -DePiep (talk) 14:00, 8 October 2018 (UTC)

The sentence "In 2017, no changes were published." in the 1st paragraph under the "Published values" section needs to be revised with the publication of

Slark (talk) 11:31, 2 February 2019 (UTC)

References

 Done. -DePiep (talk) 11:41, 2 February 2019 (UTC)

Cheers DePiep, the <ref> I cited above needs to be added to the text "2017" in the title for "Template:Standard atomic weight of the elements".

This <ref> also needs to be cited in the note column (with the note "2017") of the 14 elements whose standard atomic weights were revised in 2017 (13 Al, 18 Ar, 27 Co, 79 Au, 67 Ho, 77 Ir, 25 Mn, 41 Nb, 59 Pr, 91 Pa, 45 Rh, 65 Tb, 69 Tm, 39 Y).

▪ 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) 12:52, 8 October 2019 (UTC)

@Alexander Lozovsky: I replied at talk:argon, where you have put the same post. [2] -DePiep (talk) 13:45, 8 October 2019 (UTC)

Now: up to date and in synch with Wikidata

About atomic weight's data we are using.

• The enwiki dataset is up to date with the latest CIAAW/IUPAC formal publications re Standard atomic weight (weight?). The local enwiki s.a.w. dataset (overview) reflects the 2013-2015-2017-2019 statements and changes, refs included.

• Recently, each Wikidata element's s.a.w. property has been updated, so today the WD and enwiki values are the same! -- that is: they are the IUPAC ones. See overview and compare wikidata (which calculates any delta). -DePiep (talk) 22:21, 20 October 2020 (UTC)

Dimensionless

The physical quantity standard atomic weight (A_r) is dimensionless by definition. So: the value has no unit after the number.

Different is: physical quantity Atomic mass (m_a or m), it has unit: Da or u.

Lambiam tried to clarify this in this GF edit, but the wording was incorrect so I had to revert. It is not that "the unit is 'u' and is just not mentioned". The unit mathematically and formally disappears because the measured mass (an m so has unit u!) is devided by the purpously defined mass, the ¹²C mass (also unit u!). The devision cancelles both units, that is how it becomes dimensionless.

Sure this should be described much much better in the article and in the lede, as Lambiam initiated. Even before the "mix of isotopes" part. I myself could not create it, but others including Lambiam might give it a go. Have a nice edit. -DePiep (talk) 19:57, 26 October 2020 (UTC)

I've given it a try, also doing some shuffling of sentences and other copy editing.  --Lambiam 21:05, 26 October 2020 (UTC)

Go ahead! I am trying to explain the difficulty, here. Obviously, I could not write it myself so improvements are needed :-) -DePiep (talk) 21:55, 26 October 2020 (UTC)