Talk:Discovery of the neutron

Contested deletion

This page should not be speedy deleted as an unambiguous copyright infringement, because with all due respect, the neutron article is original and the external page in question has copied wikipedia. Check history on neutron. (Which I wrote most of this material myself...) Bdushaw (talk) 23:30, 21 March 2015 (UTC)

This new article, BTW, consists of sections being transferred over from the neutron article, per agreement from the regular editors on the Talk page. Bdushaw (talk) 23:32, 21 March 2015 (UTC)

I have removed the db-copyvio tag as placed in error. Jbh (talk) 00:01, 22 March 2015 (UTC)

Spectroscopic details of N14 spin

I think that the article must include the spectroscopic details and their analysis on the spin of N14 nucleus in relation to nuclear electrons that the neutron article doesn't mention.--86.125.167.19 (talk) 14:45, 4 April 2015 (UTC)

Name of the article - addition

I suggest an addition to the name of this article which should be called Discovery and structure models of the neutron.--79.119.211.39 (talk) 11:20, 5 April 2015 (UTC)

Archived talk pages

Most of this article was developed after extensive discussion of many of the key points on the Neutron article talk pages. This past discussion is Talk:Neutron/Archive_3 archived on those talk pages. You may consult that archive to review those discussions. If necessary, some of those discussions could be dearchived to this talk page, I presume. Bdushaw (talk) 19:48, 9 April 2015 (UTC)

Aston/amu

Not quite sure how to correct it, but the discussion about Aston should likely avoid "amu", a modern concept. He based everything off of Oxygen, declared to have a mass of 16. Mass of H is therefore 1.008, from that. Not sure how to write that, however. Bdushaw (talk) 22:15, 20 August 2017 (UTC)

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Possible developments

Just to let everyone know what I am contemplating in some near-term article developments: I suspect the article should begin with a new short section on the discovery of the alpha, beta, gamma radiations. The lede is supposed to reflect the article, and the article does not describe Rutherford's alpha radiation work. I contemplate breaking up the section now titled "Rutherford atom" into subsections or separate sections (e.g., Gold foil experiment, Isotopes, Atomic number, Rutherford atom). That section is getting a little long. I also would like to include a brief discussion of Henry Moseleys work on identifying atomic number as the number of protons. These are all important precursors to Rutherford's 1920 paper.

The newly cited article by Steuwer is quite a good one, and quite illuminating. The 1931 text by Gamow (114 p.) apparently is quite pointed on all the problems with the nuclear electrons hypothesis. The article seems to be mentioning all the right things at the moment. The vigor with which many people clung to proton+electrons is a lesson on preconceptions and belief systems of scientist! The concept became deeply entrenched with many people, including Rutherford and Chadwick - people were quite resistant to accepting the notion of a new particle. Bdushaw (talk) 08:51, 20 September 2017 (UTC)

I think the article should be more focused on the title subject. The discovery of alpha, beta and gamma radiations did not really lead to the discovery of the neutron. What was noticed at the time was that all the known massive radiations/particles (alpha, beta, proton) were charged, leading to the idea that massive neutral particles do not exist. As for isotopes, we now teach in high school that they differ only in neutron number, but historically the proton-electron model explained isotopes differently, and their existence did not lead to the discovery of neutrons.

I would start with a brief mention of gold foil and the discovery of the nucleus, followed by the proton-electron model and its problems. Dirac66 (talk) 18:00, 20 September 2017 (UTC)

Thanks - I will think about it. The lede should likely remove the mention of Rutherford's alpha particle. Isotopes seem to me, in retrospect, to be rather important to the story - that everything is in increments of one, important to Rutherford's 1920 model for the atom, and also central to the discovery of binding energy. It is a diffuse subject, to be sure - but we should stay focussed on the subject of the article, to be sure. Bdushaw (talk) 18:33, 20 September 2017 (UTC)

Yes, I see your point about isotopes. Before they were discovered, a fractional atomic weight such as Mg 24.3 was considered as a unique value for all Mg atoms, and could not have been explained by either the (p,e) or (p,n) model. Dirac66 (talk) 23:29, 20 September 2017 (UTC)

I am concerned about language - it is so easy to write things incorrectly, to allow present day knowledge to influence the text describing the situation in 1920-1921. I've corrected the article a little for this reason, in comparison to the text of Rutherford's Bakerian lecture. One thing the article is missing is a discussion of the alpha particle and that it was viewed as a constituent of nuclei, as well as a bound state of four protons and two electrons. The neutron conjecture takes a new meaning in light of this common notion - nuclei were viewed as combinations of alphas, "loose" protons, and "loose" electrons (and, after Rutherford 1920, neutrons). Meanwhile, I now have a copy of the Gamow Atomic Nuclei text from 1931 and the word "neutron" does not appear - I suspect "neutron" might have been a Cavendish Lab thing, until Chadwick's discovery. Gamow was from the Copenhagen school; the text is quite skeptical of "nuclear electrons", the problems we describe in the article highlighted. Bdushaw (talk) 16:53, 26 September 2017 (UTC)

Done for now, I think - I hope I corrected the most egregious textual errors (many by myself...). I suspect an introduction to the first section by describing the set of newly determined radiations would be useful (the new ways to probe atoms), and we need a discussion of Henry Moseleys work in establishing Z. Meanwhile, youtube gives us: https://www.youtube.com/watch?v=Cp6uovmSgKQ which is, frankly, amazing. Bdushaw (talk) 14:56, 27 September 2017 (UTC)

X++: mass 3 or 4?

Today's edits include two sentences which appear to contradict each other: Rutherford had reported on the discovery of a new doubly charged particle of mass 3, denoted the X++, interpreted to consist of three protons and a closely bound electron. ...... The X++ particle was later determined to be just a low-energy alpha particle. However the alpha particle has a mass of 4, not 3. What have I not understood? Dirac66 (talk) 15:42, 27 September 2017 (UTC)

The X++ was interpreted as mass 3 (tritium, if you will). But that was an error on Rutherford's part. It was actually an alpha. So Rutherford's conjectures were motivated from an error... Feel free to edit to clarify; thanks for the spelling correction. Bdushaw (talk) 15:46, 27 September 2017 (UTC)

It seems strange that the mass uncertainty was so large, even in 1919. The previous section says that in 1919 also, Aston obtained a hydrogen mass of 1.008 whose excess over 1 was well outside experimental uncertainty, so I would expect Rutherford could distinguish 4 from 3. Perhaps his X++ of mass 3 was based on a result so preliminary that it does not really merit mention in Wikipedia. Dirac66 (talk) 16:21, 27 September 2017 (UTC)

While I can't say I've read the 1919 paper by Rutherford carefully, I can say the (erroneous) properties of the X++ were determined by scattering methods. The mass spectrograph had the small uncertainties, but I doubt there was enough X++ to run it through a mass spectrograph. Ordinarily, one would ignore the X++, I agree, but in this case it proved to be the thing that motivated the conjectures regarding the neutron and deuterium. Its in the Bakerian lecture paper and carefully described by Steuwer in his Electron-Proton hypothesis paper. These considerations indicate the reasons later on why there was still resistance to accepting the neutron as its own particle, and not a proton-electron pair. Bdushaw (talk) 16:34, 27 September 2017 (UTC)

Thanks. I have inserted a few words to make it clearer that the 3 was an incorrect value by ER. (And that tritium was not really discovered in 1919!) Dirac66 (talk) 20:30, 27 September 2017 (UTC)

More word smithing today; hopefully the section is settling down; I operate from the notion that this is an encyclopedia hence things have to be simple and clear, and one cannot rely on the reader to know or otherwise figure out stuff (I keep 8th graders in mind). I note that many of the old cited articles can be viewed here, although that looks to me like a clear copyright violation. (Articles from the publisher require a fee or otherwise a subscription.) Still, it is nice to be able to instantly verify sources! Bdushaw (talk) 12:59, 1 October 2017 (UTC)

Introductory paragraph on radiation

I've included an introductory paragraph on radiation. It seems to me the article needs such a paragraph. What I wrote is merely preliminary, however - feel free to edit for polish, etc. It is likely the paragraph could be better sourced - the book Inward Bound would be a good one to cite here (I don't have it handy, however.) Bdushaw (talk) 15:46, 11 October 2017 (UTC)

Chadwick portraits

I am wondering about the present portrait of Chadwick we are using. It is part of a photo that has L. Groves to Chadwick's left - must date to the 1940s. I am wondering if a better, more contemporary, portrait of Chadwick could not be clipped from the 1933 Solvay conference photo. Then the Chadwick/Groves photo could perhaps be included at the bottom of the article next to the concluding paragraph. (and I am unsure about the two images presently dangling at the end of the article) Bdushaw (talk) 07:10, 12 October 2017 (UTC)

The new picture may be more contemporary, but it's also dour and fuzzy... --Ørjan (talk) 05:54, 16 October 2017 (UTC)

Well, its not perfect, to be sure... But the other one had its own problems (Chadwick was not looking at the camera and had his eyes closed; he looked dour there too! He was overly dressed in the suit, and it was part of the famous photo of him sitting next to Groves). We could do with a better photo, but for conveying what Chadwick looked like in 1932 it seems to me to be a bit better. We can go back to the Chadwick-Groves photo if there is a consensus for that. I thought about including that photo, with Groves, at the end of the article, but there are too many images (so many images, so little space). Bdushaw (talk) 07:25, 16 October 2017 (UTC)

Moseley's Law

I've made a start at a new section on this important topic. I hope the section will be brief - I have a general notion of the topic, I think its important, but am still a little foggy as to the basic facts... K and L X-ray lines, the Bohr model, and the required Z matches the atomic number in the periodic table, ergo, Z is atomic number. Its easy to take all this for granted these days, but it was anything but back in 1911! I will work at it...feel free to contribute... Bdushaw (talk) 15:08, 23 October 2017 (UTC)

While never finished, of course, I believe the recent Moseley contributions were the last of the changes and additions I wanted to make. The one event that has only a slight nag at me is that of Rutherford "discovering" the proton in 1919. Its described that way, but it really was that he managed to knock protons out of nuclei with fast alphas and record that. I haven't the interest or energy to pursue the issue, nor does it seem related to the neutron - except perhaps that similar techniques were later used to detect the neutron. In any case, signing off for now. I've contemplated nominating the article for "Good" status - that would entail a lot of work, and perhaps the article should simmer a bit to show that it is stable. Bdushaw (talk) 19:38, 26 October 2017 (UTC)

At Proton#History we find the clear statement In 1917 (in experiments reported in 1919), Rutherford proved that the hydrogen nucleus is present in other nuclei, a result usually described as the discovery of protons. I don't think it is necessary to repeat that in this article. Dirac66 (talk) 21:51, 26 October 2017 (UTC)

Why remove page number?

One edit summary today reads remove page number from byrne ref. Is there is a special reason for removing this particular page number? Normally a page number would help readers find the information cited. Dirac66 (talk) 21:17, 6 November 2017 (UTC) n

Yes...the reference is used elsewhere, however, to cite other facts on different pages. I suppose there are systems that let you make a citation and then cite specific pages within it...but I don't know how to do that! Anyways, that's why.

I am thinking of drawing a figure of the Chadwick experiment as an illustration. There are many by google search, but none seem to have an accessible license. Its easy enough. Bdushaw (talk) 21:52, 6 November 2017 (UTC)

I see Pais is referenced in another place, giving page 299, or something. Not sure what to do - have a separate citation for each page referenced? Rework the article to use a different citation system? Use a page-agnostic citation? There are other places that reference would be a useful citation. The first citation to Pais is a "crude" citation. The article could likely use a thorough review of the citations...ugh. Bdushaw (talk) 22:59, 6 November 2017 (UTC)

There are 2 Wikipedia tools which you might consider as possible solutions to this problem. See Template:Rp (= reference page) and Template:Sfn (= shortened footnote). Dirac66 (talk) 01:15, 7 November 2017 (UTC)

Trying Rp for now as seemingly most suitable for the circumstances...but it looks a might strange to me... Bdushaw (talk) 21:33, 7 November 2017 (UTC)

Presumably Wikipedia readers get used to Rp and learn quickly that the extra number is a page. I think what you have done for the Pais cites is fine. Now there are still the Byrne cites if you want to add the pages (I do not have the book); one was p.5 (also!) and the other did not yet have the page. Dirac66 (talk) 22:19, 7 November 2017 (UTC)

I see Byrne - I have that book, but not the Pais book (with me anyways). Also Stuewer. My plan is to putter way at the references, one small step at a time...There are sundry problems/omissions. The article has only 2-3 references with multiple citations, hence Rp seems appropriate. If I can get through that, then we might perhaps put the article up for Good Article status (which is not easy!). Bdushaw (talk) 22:32, 7 November 2017 (UTC)

As I survey the sundry citations...perhaps some discussion and consensus are in order before I spend too much time on revising citations. Firstly, I noted that there are a variety of coding styles employed in the citations for the article. My first thought would be to convert them all to a common form. Or is it fine to have different forms employed in an article (bear in mind the ambitious goal of "good article" status)? We had agreed on a form for specifying pages, but I have a few technical problems there. Some books (Pais) I do not have, while other books (Byrne) I have, but in Kindle form, which has no pages. I am thinking that perhaps citing the chapter, rather than the page, may be the way to go ("Ch 5" or "Sec 12", say), if the Rp coding would allow that. Some of Pais can be seen on Amazon as a preview. Interestingly, page number might become a thing of the past, if we head towards the all digital age. (I am home with a cold today, hence bored...) Bdushaw (talk) 15:06, 14 November 2017 (UTC)

I favour specifying page numbers whenever possible, since they may help at least some readers (without Kindle!) find the relevant material in the source. Now and then I have tried to locate information from a footnote with no page, and it can be very frustrating indeed flipping through a PDF. I don't think a common form is particularly useful, as long as the information for each reference is accessible. Dirac66 (talk) 02:49, 15 November 2017 (UTC)

I'll use this section for a general discussion of citations. Regarding the lede, I am somewhat puzzled by whether citations should be given there, or if citations later in the article could be relied on. Is there a policy for citations in the lede? It would be a matter of copy-pasting citations from later in the article into the lede, I should think. I also think the lede should perhaps be expanded a bit to encompass all the main points of the article. Bdushaw (talk) 12:09, 17 November 2017 (UTC)

Polonium

I've been contemplating polonium in the context of this article. There are several interesting facts that I am unsure if they should be included in the article. There are also boundaries of facts, opinions, and original research that are rather blurry. These are: Polonium is a somewhat rare substance, quite rare in 1932, that is highly radioactive - it is an alpha emitter, with alpha energies of 5.3 MeV (Po-210). It is also highly toxic, even in tiny amounts, because of its radioactivity (c.f., modern-day assassination plots). It seems to me not by accident polonium was used in this case - an intense radioactivity of alphas used to blast away a large flux of neutrons out of beryllium. Polonium is a product of radium decay; it has a half life of 138 days or so. It was quite rare in 1932, as I said, and indeed the Curies had most of the world's supply of it. The polonium at the Cavendish had been acquired by Norman Feather in Baltimore from a hospital there. They were using radium to treat cancer/tumors and had a great pile of expired radium capsules. Feather got them to give the expired capsules to him while he was in Baltimore for a postdoc, and he shipped the vials of polonium home to the Cavendish in his suitcase. Thus, at the time of the Curie experiment, the Cavendish had sufficient polonium on hand to make the measurements to discover the neutron. Much of this was described by Feather during his API interview, cited in the Feather article. Anyhow, I thought I would put this backstory down - perhaps some of it ought to be in this article. Bdushaw (talk) 19:00, 12 November 2017 (UTC)

I would add this instead to the history section of the polonium article at Polonium#History. Dirac66 (talk) 21:56, 12 November 2017 (UTC)

Looking through my 1931 Gamow text book, I see that the results of Bothe and Becker made it in. "The excitation of nuclei by collision with incident alpha-particles was recently investigated by Bothe and Becker (1930) who succeeded in observing rather hard gamma-radiation from a number of light elements bombarded with alpha particles from polonium." Then another couple of pages describing the curious energy of those gamma rays. Amusing and illuminating. Its Be-9, atomic number 4 - the small atomic number was likely important, since the Coulomb repulsion was reduced and the alphas could reach the nucleus. Adjacent Li and B also work (according to Bothe and Becker) but are much less efficient than Be. Bdushaw (talk) 10:47, 13 November 2017 (UTC)

Perhaps this article could include one sentence beginning "Polonium was used as a source because ...". Dirac66 (talk) 14:35, 13 November 2017 (UTC)

Chadwick and Goldhaber: n mass

While I think I have interpreted the Chadwick/Goldhaber paper correctly in how they determined the mass, I am somewhat puzzled... If we use present-day values for the masses and binding energy of the deuteron, the equation doesn't seem to balance: deuteron mass 2.01410 u, binding energy 0.002388 u, proton mass 1.00727 u, neutron mass 1.00866 u, which make the two sides of the mass equation differ by 0.000558. This is not exactly small, given the uncertainties of the modern values; something else must be going on. CandG also used 1.0081 as their proton mass, which is rather off the mark. The various values seem awfully shifty and not particularly satisfying. Bdushaw (talk) 12:05, 17 November 2017 (UTC)

Never mind...I used the isotope mass for deuterium (2.01410), rather than the mass of the deuteron (2.013553). Never trust Wikipedia. ( :) ) Bdushaw (talk) 13:03, 17 November 2017 (UTC)

To be fair, there are also occasional errors in other sources such as books and journal articles. Never trust anything without checking. Dirac66 (talk) 16:55, 17 November 2017 (UTC)

(I was speaking facetiously...making fun of the attitude that many people seem to have towards W.) Thinking about the issue a bit more, it occurred to me that the issue is perhaps not trivial. Chadwick and Goldhaber likely were using masses for the deuteron and proton that included the mass of the electron. That is, they made no deliberate attempt to be sure the electron had been stripped from these nuclides. This is likely why their mass values for these are larger than the present-day "bare" values. Luckily, the electron mass cancels in the simple mass calculation. A point that seems overly tangential for this article. Bdushaw (talk) 20:51, 18 November 2017 (UTC)

GA Review

This review is transcluded from Talk:Discovery of the neutron/GA1. The edit link for this section can be used to add comments to the review.

I'll do this one. Reviewer: Chiswick Chap (talk · contribs) 15:44, 5 December 2017 (UTC)

Comments

This is a thorough and well-cited article and I have few comments to make on it.

• "electromagnetic radiation (light)": ahem.

• In the same sentence as "(light)", a list introduced with ":" should have items separated by ";".

• "Rutherford developed a mathematical model that accounted for the scattering." Is that the same model as the previous sentence? If so, make that plain (and move the citation down); if not, add a citation.

• You might like to use a photo of Aston in the isotopes section and of Moseley in the Moseley's law section.

• You might also use a photo of one of Aston's mass spectrometers. File:Early Mass Spectrometer (replica).jpg.

• An ISBN or other ID should be provided for each book cited. The Story of Spin's is 978-0226807942, for instance. For Weak interactions and nuclear beta decay you can use the OCLC=954181689. Einstein: His Life and Universe is 978-0743264747 and its OCLC is 228652687. There are more.

Minor details

• In the lead, the boldface title phrase must not include wikilinks.

• Please link James Chadwick in the first image caption.

• "a mass value 1.008." Wouldn't that be "a mass value of 1.008." ?

• "hence precise measurements were required." That was and remains true of all physics experiments. What is intended here is "exceptionally precise".

Editor Replies

Thanks for giving the article a review! I've gone over your comments/suggestions and I believe I have responded to all of them, which they are minor enough. I think I got all the book ISPN's (Gamow's 1931 book has nothing, however - a book that was outdated and shown to be all wrong within a year!!!), but I might have missed one. I am reluctant to include photos of Aston and Moseley - mainly because it would elevate them to the level of Rutherford/Chadwick/Fermi, which they were not. Also because the article then seems to have too many people - an article about the people who discovered the neutron, rather than neutron itself. I've included the mass spectrometer photo however - I've tried to highlight how primitive this all was, hence amazing, which this image is consistent with. Bdushaw (talk) 16:55, 6 December 2017 (UTC)

Summary

This article is easily up to the required standard and I'm glad to have been able to suggest some small improvements to a fascinating and human story. If you're thinking of going on to FAC, I'd advise you to take great care with polishing the references. Meanwhile, my congratulations on an excellent article, and I'd like to invite you to review one or two of the many interesting articles awaiting a GA reviewer. Chiswick Chap (talk) 18:45, 6 December 2017 (UTC)

Recent edits by 老陳

User 老陳 has made a number of editorial changes that I am not sure I agree with. Fighting the urge to put the article back as it was, I bring the issue to this talk page for a consensus discussion. The issues are perhaps minor, but it seems to me a number of minor, but not up to par, changes lead to a drift in article quality. I think I prefer Gold foil experiment as the first section heading, I think "In Aston's experiment..." is not correct (there was no experiment per se), etc. As a general question, in a number of articles the given url in references are being removed if there is a doi present - is that the accepted approach? A bot is doing that. I sometimes use a url to an article pdf that may not be accessible from the journal publisher (whether proper or not, its far more convenient). Some of the changes are good, so a blanket revert is not suggested. Bdushaw (talk) 06:34, 5 September 2019 (UTC)

Re first section heading: there are 2 paragraphs of similar length and Gold foil experiment describes only the second. Perhaps we could divide the section in two: Discovery of radioactivity and nucleus AND Gold foil experiment.

Why was Aston's work not an experiment? He built a new type of instrument and tried to measure isotopic masses with it, and it worked. It might not have worked. I call that an experiment.

I agree that 2 internet addresses are better than one (provided they are different). If one disappears from the internet or is hidden behind a paywall, the other may still be available. Dirac66 (talk) 21:30, 7 September 2019 (UTC)

I'll resist the urge to hoover over the article...and let wikipedia do its thing. It's not easy when one has worked hard on an article! I'll follow some of the threads you suggest. I think by the time referred to in the article, Aston was making measurements, the initial experiment having been successful. It was not my intention to include discovery of radiation in any degree in this article, being too far afield from the topic at hand, but in for a penny in for a pound. I'll split the section as you suggest - I liked the section heading highlighting the astonishing gold foil experiment, but we can have our cake and eat it too, I think. With these edits, I think I will stand down from the article and let it go. Its likely not good for an editor to be too heavily invested in an article, etc. Thanks for the reply and the latest edit RE Soddy. Bdushaw (talk) 07:54, 8 September 2019 (UTC)

OK...done. I note that there is perhaps room now for development of a better discussion of discovery of radioactivity (e.g., M. Curie, pitchblende, etc.) and perhaps the extent to which radioactivity itself demonstrated the existence of atoms. With that, I will look away from the article and send my child out into the cold, dark, dangerous wikipedia world :) Bdushaw (talk) 08:06, 8 September 2019 (UTC)

A final note: the statement on measurement of binding energy was removed. It was a bit awkward to be sure, but this was an important precursor to the later section on the binding energy of the deuteron, etc. By introducing binding energies at this early stage, which is the time that was sorted out, the later section makes more sense (that is, "binding energy" does not come out of the blue in the later section). I suggest restoring the sentence, in perhaps better form. Oh what a tangled web we weave, when first we practice to revise wikipedia articles. Bdushaw (talk) 08:18, 8 September 2019 (UTC)

Theoretical contributions by Nathan Rosen and Harrie Massey

I see here on Wikipedia some pages of authors Nathan Rosen and Harrie Massey having developed some theoretical contributions re the neutron as proton-electron combination in 1931-1932, articles which I have encountered in Physical Review (https://doi.org/10.1103/PhysRev.37.1579) and Proceedings of the Royal Society.--109.166.135.197 (talk) 12:06, 28 November 2019 (UTC)

I think these sources could/should be cited to add more details in the article.--109.166.135.197 (talk) 12:12, 28 November 2019 (UTC)

I see that Massey is mentioned in article, but the info extracted from his article is very little.--109.166.135.197 (talk) 12:50, 28 November 2019 (UTC)

Number of pages in source 48

Which are numbers of the 3 cited pages from source 48, A. Brown, (1997) The Neutron and the Bomb: A Biography of Sir James Chadwick?--109.166.136.139 (talk) 23:29, 29 November 2019 (UTC)

Restoration from recent edits

Edits in recent months have removed or added text that seem to me to be missing the mark, while oftentimes introducing logical or grammatical problems. The edits were given no justification or argument, beyond a vague "improve content". I have restored some of these edits, as noted below, with comments as to why I restored or corrected the text. This was not easy. I tried to retain the citations as much as possible. I note that the article is a "Good" article, so editors should be particularly careful to proofread their changes for grammatical correctness.

• Start of Moseley section. Logical/reorder correction, remove extraneous wording
• Moseley section. The wording seemed unencyclopedic, being more like a story. Corrected grammatical problems ("this" needs to have "this (something)"). Restore logical ordering of sentences. Erroneous to focus on only K-alpha. K-alpha radiation needs a brief definition, etc.
• Moseley/Bohr model. The logical order was first Moseley empirical equation, followed by application of the Bohr model to explain/derive it. That has to be the order in the text.
• Meitner/Hahn work prior to WWI. M&H worked on the radiation of heavy nuclides for about 20 years around WWI. This fact is an important precursor to the discovery of fission. Indeed, Meitner had to convince Hahn to take the work up again in the late 1930s.
• Rutherford atom. Correct awkward wording. "scattering of alpha particles from heavy nuclei", yes?
• Rutherford predictions. Text was removed that rendered the narrative illogical (???). Restored.
• Klein paradox. The topic here is somewhat advanced, involving relativisitic QM and pair creation. I can't say I fully understand the paradox, which I've struggled with, but I am fairly certain the text I removed is just confusing. I adopt a minimalist approach.
• Binding energy. I've restored the statement regarding the energy of beta radiation. This is an important point, and I believe we discussed such questions rather vigorously when this article was still part of the Neutron article.
• Final paragraph of "Problems". General grammar/language problems. Problem of continuous distribution of beta radiation energy needs introduction. "many researchers soon began to realize" - this statement is mostly nonsense, certainly vague. The suggestion of the violation of energy conservation, a desperate measure, was most certainly related to the peculiarities of the quantum mechanic revolution.

Bdushaw (talk) 10:28, 6 December 2019 (UTC)

Klein paradox revisited

I previously removed this text regarding the Klein paradox: high-energy electron approaching a potential barrier has a high probability of passing through the barrier by energy-gaining transformation from a particle of positive mass into one of negative mass. I didn't have access to references at the time, but consulting the Gamow 1931 monograph now, I see the following quote on page 5 ...although the electron has not sufficient energy to leave the hole [of potential energy] as a particle of positive mass, it will nevertheless immediately escape by changing the sign of its mass. So although in the quote I removed I object to "high-energy" and "energy-gaining" adjectives, it was roughly correct. Gamow was at Copenhagen at the time and right in the thick of the discussions of this paradox.

But it is also not physically correct... The idea that the electron "escaped" by transforming into a negative energy electron made no sense to me. What is meant, in modern parlance, is that as the electron approaches the potential barrier, positron-electron pairs are created, with the 1st and 2nd electrons forming a current away from the barrier back into the nucleus, and the positron continuing beyond the barrier and escaping. This paradox was near the birth of field theory, which was able to resolve the paradox (the seething continuum of "sea" particle-antiparticle creations, etc.) I suppose the paradox suggests there should be an infinite radiation of positrons from a nucleus, coupled with an energy catastrophe within the nucleus, if there were electrons confined within it.

All this seems far too much to explain in the article without causing further confusion, seems to me. Do we describe what people incorrectly believed, then try to give a corrected (field-theoretic) explanation? I am inclined to leave the text short and somewhat vague. The Klein paradox article, however, should likely have a section on its role in regards to nuclear electrons. (Perhaps a job for someone else.) Bdushaw (talk) 04:39, 8 January 2020 (UTC)

Santiago Antúnez de Mayolo presented his work "The constitution of Matter"

I am not sure what to do with this new addition to the article, but tend toward removing it - the new addition credits Mayolo with the original suggestion of a neutral element in the atom. Perhaps true, but Wikipedia is not the place to make this acknowledgement (were there others elsewhere making similar claims?). I would prefer the point was made in a reliable, historical research work, rather than the citation to the conference proceedings dating to 1924, wherein the reader makes his own determination of the result and its importance; seems like OR. The sentence is also out of place. Comments? Bdushaw (talk) 01:06, 6 December 2020 (UTC)

I've removed this recent addition. The statement is based on a primary source that is weak - a single conference proceedings from 1924. It is original research - we are to infer from this primary source that Mayolo gave a compelling case for the existence of the neutron in 1924; far better to cite a secondary source that acknowledges such a contribution and puts it in context. I know of no such source (see the citation list for this article, for example), having never heard of Mayolo until now. (The sentence was also out of place, but never mind.) Bdushaw (talk) 06:20, 9 December 2020 (UTC)

User AHaikkuu.2468 restored the material previously removed, and I have removed it again. The material does not have sufficient sourcing for its inclusion in this article. Bdushaw (talk) 16:59, 16 January 2021 (UTC)

Actually the edit in question did not say that Mayolo's suggestion in 1924 was original. And we know that it was not, since this article already mentions Rutherford's similar suggestion in his 1920 Bakerian lecture, as well as Harkins' suggestion in 1921. So it would not be surprising that after 1921, Mayolo in 1924 and perhaps other people also made similar suggestions. But since they were not original AND no experimental proof was yet available, then I agree with you that Mayolo (and possibly others) are not notable enough to note in this article. Dirac66 (talk) 17:34, 16 January 2021 (UTC)

First five sections

The first five sections of this article don't seem to fit under this article. While each section describes experiments and theories that were necessary to discover the neutron, they shouldn't take up more than a page of the article. Cassie Schebel, almost a savant. <3 (talk) 13:56, 9 September 2022 (UTC)

Thanks for taking a look at the article and giving it consideration. I do not agree with your assessment however. The article is attempting to show how neutrons came to be discovered, building from the "primordial soup" of basic discoveries of radiations and chemical elements. In the first 3 decades of the 20th century the issues were murky and confusing indeed; but the confusion is relevant to why the neutron's discovery was so important. These first five sections cover several profound discoveries in a quite brief manner (IMO). Further, these sections introduce concepts and language that are later used to describe the neutron as radiation and the experiments used to discover it. (As an aside there are those who question the existence of neutrons, etc.; a proper, clear case has to be made!) Bdushaw (talk) 12:06, 16 September 2022 (UTC)

I would also point out that we have an another article entitled simply Neutron, which has a much briefer section on the Discovery for those readers who want to arrive quickly at the modern understanding of the neutron. This article on the other hand is for those who want to know more about the discovery. Dirac66 (talk) 01:23, 17 September 2022 (UTC)

That makes sense, thanks. Cassie Schebel, almost a savant. <3 (talk) 21:11, 31 October 2022 (UTC)