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==John Dalton==
I've done a lot of googling on the net trying to find precise details on how exactly Daltin arrived at his atomic theory, and some of the information has been contradictory.  When I wrote this section, I put nitric oxide and oxygen as one of the pairs of gases he studied.  Some articles said Dalton referred to the former as "nitrous gas", and that this gas was really nitric oxide (NO).  The equations and ratios I wrote were an educated guess on my part rather than a quotation from what Dalton actually did.  However, another wikipedian rewrote it to be nitrous oxide (N<sub>2</sub>O), which changes the equations somewhat.  Are there any experts on Dalton's life and work who can give a definite answer to this?  Could some student here please ask their chemistry professor?


I removed this paragraph:

:In some cases the study of a property at atomic level is very complex and easier results are obtained with a study at a bigger scale. This does not means that atomic theory does not work in these cases. The problem is the [[mathematical complexities]] given by treating such problems with the atomic theory. Till nowdays there are no cases where atomic theory does not work, there are only cases in which the result is more easily obtained, in the limit of the wanted approximation, with easier theories. Despite that it may be of some worthness to point out that a general vision should always kept and considered, and to consider the world or the entire universe only as series of atoms is reductive.

Aside from its very strange usage ("Till nowdays", "some worthness"), I think this is factually incorrect. There are many cases where atomic theory does not work, which is why a further reduction to quantum mechanics was required. I would be happy with a rewriting of this paragraph to express the fact that large-scale abstractions are still useful for thinking about things, as long as it is correct. [[User:Brighterorange|Brighterorange]] 7 July 2005 23:25 (UTC)

:You did the right thing.  It was too generally worded to get any interesting meaning out of it, its vague. Re-write if you wish. [[User:Linas|linas]] 04:35, 10 July 2005 (UTC)

I removed a small paragraph mentioning an early, discarded theory of cubical atoms from the last section.  I believe this article should focus only on the chain of developments that led to modern accepted atomic theory (in particular, give the reader a basic idea of how scientists figured it out).  Dead ends and tangents can make things a little confusing.[[User:Kurzon|Kurzon]]


You really do have a great article, but I have one point...it was Dalton's "Atomic Theorie"
he really did spell it like that...[[User:74.237.244.61|74.237.244.61]] 22:26, 18 February 2007 (UTC)

I've made some corrections and additions requested by the first writer in this section.  The writer's "educated guess" was very close to the truth, but not quite, as the multiple for Dalton was nitrous air, not oxygen.  Dalton's "nitrous air" is nitric oxide, not nitrous oxide (the latter of which he called by that name).  Dalton spelled the word "theory" just as we do.   [[User:Ajrocke|Ajrocke]] ([[User talk:Ajrocke|talk]]) 14:33, 13 February 2008 (UTC)

I think he just took the hint from Guy-Lusaac law of combining volume. But, it is hard with out knowing the starting point. The table he got is way off. [[Special:Contributions/76.219.230.165|76.219.230.165]] ([[User talk:76.219.230.165|talk]]) 03:07, 19 January 2013 (UTC)

==Visualizability==
"Up until the late 20th century, atoms could not be directly observed. Beginning as a purely philosophical concept, their existence and nature were explored indirectly by correlating knowledge gained through various scientific experiments over the course of the past few centuries."
I'm not sure what is meant here by "directly observed" — they can still not be "directly" observed any more than they once could. They can be indirectly observed, and with far better precision than they could before, but "directly"? Though I am usually averse to Bohr-style philosophical discussions of what "observation" means, when we are talking about things as small as atoms I think it becomes impossible not to be very careful in our terminology. --[[User:Fastfission|Fastfission]] 19:51, 15 October 2006 (UTC)

Don't field ion microscopes count as direct observation? [[User:Kurzon|Kurzon]] 14:36, 17 October 2006 (UTC)

== Philosophical Atomism vs. Atomic Theory. ==

This is already a great article.

I have a problem: Philosophical atomism addresses the concept that the matter in the universe is composed of indivisible units. This philosophy is not invalidated by "splitting the atom". Basically, the fact that we can split an "atom" merely means that we assigned the name "atom" to the wrong physical unit.

The definition of an "atom" according to the philosophers is "an indivisible entity." It is not the fault of the  philosophers that Dalton and other early chemists incorrectly attached the word "atom" to an entity that we later discovered to be divisible.

==GA Passed==
Congratulations, this article has passed the GA nominations. As a suggestion I would suggest having 2-3 citations in each section. [[User:Tarret|Tarret]] 19:25, 28 October 2006 (UTC)

===GA sweeps review===
Re-reviewing the article on 29 August 2007 to confirm that it still meets the [[WP:WIAGA|GA criteria]]. Other than a few minor reference formatting fixes, this article continues to meet the criteria, and will continue to be listed as a [[WP:GA|Good Article]]. [[User:Derek.cashman|Dr. Cash]] 16:47, 29 August 2007 (UTC)

==More on quantum model needed==
Most of this article is about the redundant atomic theories, more needs to be added about the current accepted model
:That's what the [[atom]] article is for.  This article is about the chain of discoveries that led to the current model, and the historical models begot at each stage.

== Isotopes ==

The discovery of isotopes is commonly attributed to [[Frederick Soddy]] (at least he is the one who got the Nobel Prize for it). I don't know much about the claim that it was Thompson, but if there's something to it the article should also mention Soddy and explain. If not, the attribution should be replaced by the correct one. -[[User:Itub|Itub]] 18:37, 26 March 2007 (UTC)<small><small>Small Text</small><small><small>Small Text</small><small><math>Small Text</math>[[Media:#REDIRECT [[Example.ogg]]<br /><s>Strike-through text</s>]]</small></small></small>
:Well, Thomson generated the DATA for neon, but he didn't interpret it correctly at first. It sat there until 1920, when somebody realized what it was. There's also a difference between the guy who first understood that there could be isotopes of LIGHT and STABLE elements (like neon) vs the heavy and radioactive stuff that everybody was working with. I'll read INWARD BOUND on the subject and see if I can sort it out a bit better.[[User:Sbharris|<span style="color:blue;">S</span>]][[User:Sbharris|<span style="color:orange;">B</span>]][[User:Sbharris|H]][[User:Sbharris|arris]] 18:52, 26 March 2007 (UTC)
[http://nobelprize.org/nobel_prizes/chemistry/laureates/1921/soddy-lecture.pdf Soddy's Nobel Lecture] and [http://nobelprize.org/nobel_prizes/chemistry/laureates/1922/aston-lecture.pdf Aston's Nobel Lecture] are illuminating. There were many "discoverers" of isotopes in the experimental sense, but Soddy was the one who got the credit for coming up with the concept and clarifying the confusion caused by the various decay products of uranium and thorium. Apparently Thomson was indeed the discoverer of isotopes of light elements, but the isotope concept was mostly formed already based on the radioactive elements. Thomson's former pupil, Aston, got the Nobel Prize for improving the technique and applied it to the discovery of isotopes of many other elements. Note, however, that the importance of Thomson's discovery had already been recognized by Soddy in 1913. He said "The discovery is a most dramatic extenions of what had been found for elements at one extreme of the Periodic Table to the case of an element at the other extreme, and strengthens the view that the complexity of matter in general is greater than the periodic law alone reveals". --[[User:Itub|Itub]] 11:30, 27 March 2007 (UTC)

I would like to suggest that at the atomic level the complexity of the matter involved is not nearly as complex as are the conceptions and mathematics dreamed up by people who are trying to explain it.[[User:WFPM|WFPM]] ([[User talk:WFPM|talk]]) 02:55, 4 May 2010 (UTC)

==Grammar Question==
Is this a sentence? ''Or, in a nutshell, the idea that all things are made of atoms.''  <small>—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:Anthon01|Anthon01]] ([[User talk:Anthon01|talk]] • [[Special:Contributions/Anthon01|contribs]]) 20:44, 23 January 2008 (UTC)</small><!-- Template:Unsigned --> <!--Autosigned by SineBot-->

: I'm going to fix it. [[User:Anthon01|Anthon01]] ([[User talk:Anthon01|talk]]) 21:48, 26 January 2008 (UTC)
::Please fix this as well. such 
::as carbon dioxide could divided, as opposed to "elementary atoms". [[User:Luban the truth|Luban the truth]] ([[User talk:Luban the truth|talk]]) 17:52, 15 July 2023 (UTC)

== Looks like error ==

I'm just learning English, but from the sentence "Further experimentation by Rutherford found that the nuclear mass of most atoms exceeded that of the protons it possessed" I made a conclusion that the mass of an atom is greater than the sum of mass of separated protons. The matter is that the mass of an atom is less than sum of separate nucleus, because some part of the mass was converted to binding energy. <small><span class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:82.207.2.194|82.207.2.194]] ([[User talk:82.207.2.194|talk]] • [[Special:Contributions/82.207.2.194|contribs]]) 07:15, 24 February 2008</span></small><!-- Template:Unsigned -->

:The sentence refers to the understanding of the nucleus prior to the discovery of the neutron (which makes up more than half the mass of alomost all nuclei) and is unrelated to the more recent concept of binding energy. [[User:Vsmith|Vsmith]] ([[User talk:Vsmith|talk]]) 15:33, 24 February 2008 (UTC)

== Confusing sentence introducing uncertainty principle ==
The article says, "Since a wavefunction incorporates time as well as position, it is impossible to simultaneously derive precise values for both the position and momentum of a particle for any given point in time," but I am not sure what this even means.

An object containing information about time and position has absolutely nothing to do with uncertainty principle. For example, a trajectory, or, for a real life example, your GPS trace contains information about both time and position but to the idealization done in making these, both position and momentum are precisely known.

IMHO, a better introduction to uncertainty principle should begin from the fact that matter is "wave"---and waves, whether it's classical like water waves or quantum mechanical like matter waves, cannot have both the well-defined momentum (which is related to the wavelength) and well-defined position (which is related to localization).  <small><span class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:Novakyu|Novakyu]] ([[User talk:Novakyu|talk]] • [[Special:Contributions/Novakyu|contribs]]) 03:23, 21 December 2008 (UTC)</span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot-->

We're not talking about where a particle is, because it is where it is. Were talking about where a particle can be measured to be and with what accuracy of measurement.[[User:WFPM|WFPM]] ([[User talk:WFPM|talk]]) 03:33, 4 May 2010 (UTC)

== Perrin, Mach, brownian motion, Feyman ==

This entry is regrettably silent about [[Ernst Mach]]'s skepticism re atomism. It has only one brief paragraph on how Einstein's paper on [[brownian motion]], and [[Jean Perrin]]'s careful estimate of [[Avogadro's number]], convinced almost everyone by 1910-15 that atoms were indeed real. Also, when Feynman was asked to state the single most important scientific fact discovered from Galileo onwards, he said "the world is made of atoms."[[Special:Contributions/132.181.160.42|132.181.160.42]] ([[User talk:132.181.160.42|talk]]) 01:31, 21 April 2009 (UTC)
:Please [[WP:BOLD|feel free]] to edit the article, provided that any new or changed material is supported by [[WP:RS|reliable sources]]. [[User:Finell|Finell]] [[User_talk:Finell|(Talk)]] 01:39, 21 April 2009 (UTC)
:There are far too many dead-end theories in the study of matter.  This article concentrates on the chain of events that genuinely pushed modern accepted theory as we know it.[[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 20:33, 20 August 2009 (UTC)

==Leucippus the ‘father of atomic theory’ nowhere to be found?==
I find it strange that Leucippus, the originator of atomic theory, and his followers Democritus, Epicurus, Lucretius, are nowhere to be found in an article on ‘atomic theory’? I do note that he was in the original  [http://en.wikipedia.org/w/index.php?title=Atomic_theory&oldid=5267147 2004 stub] version, but seems to have been removed, to the relegated [[atomism]] article. When someone thinks ‘atomic theory’ the first names that come to mind are either Leucippus (or Democritus) or Dalton. I would suggest someone do a rewrite of this article to reflect this simplicity. The following timeline I wrote up today might lend some guidance on the basic framework of atomic theory:

*[http://www.eoht.info/page/Atomic+theory Atomic theory] – Encyclopedia of Human Thermodynamics

I hope this input helps? --[[User:Libb Thims|Libb Thims]] ([[User talk:Libb Thims|talk]]) 23:54, 8 July 2010 (UTC)

:I agree and I've added a section on [[atomism]]. <b>[[User:Audacity|<span style="color:black;">Λυδ</span>]][[User talk:Audacity|<span style="color:blue;">α</span>]][[User:Audacity|<span style="color:black;">cιτγ</span>]]</b> 00:57, 9 December 2012 (UTC)

==Lochschmidt==

I was reading the article about [[Johann Josef Loschmidt]], and it says that Lochschmidt estimated "in 1865 the size of the molecules that make up the air:[2] his result was only twice the true size, a remarkable feat given the approximations he had to make."
I jumped to this article, because I was hoping to find a description of what method he was using 1865, but there is no reference at all to this guy.  Does anybody know something more? Thank you. If relevant, maybe it could also be added to the historical part in this article.
[[User:KlausN|KlausN]] ([[User talk:KlausN|talk]])  <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|undated]] comment added 20:24, 10 September 2010 (UTC).</span><!--Template:Undated--> <!--Autosigned by SineBot-->


==Controversy==

I added the section on the controversy about the existence of atoms. I thought this should be a separate article as it spoils the flow a bit, but the editors would not allow a new page so I have put it in here.  <small><span class="autosigned">— Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:Mathew Rammer|Mathew Rammer]] ([[User talk:Mathew Rammer|talk]] • [[Special:Contributions/Mathew Rammer|contribs]]) 20:00, 4 March 2012 (UTC)</span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot-->
:I removed it because it's tangential.  There are lots of dead end theories, too many to mention.[[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 20:31, 19 December 2012 (UTC)

==history of science==

Science evolves and changes. Vitalism should be included as part of that change in this article. It should link in a way that allows tangenital stuff to be reached by linking off page, not removed to only have long equations.  <span style="font-size: smaller;" class="autosigned">— Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/88.117.37.20|88.117.37.20]] ([[User talk:88.117.37.20|talk]]) 20:43, 1 December 2013 (UTC)</span><!-- Template:Unsigned IP --> <!--Autosigned by SineBot-->

== Animation for Bohr model ==

In the animation for the Bohr model, the linear velocity in the outer orbit appears to be higher than the linear velocity in the inner orbit. In my understanding of the Bohr model, it should be the other way round: the linear velocity should be inversely proportional to the radius of the orbit.
[[User:Robamler|Robamler]] ([[User talk:Robamler|talk]]) 11:15, 4 August 2014 (UTC)
:OK, [[User:Robamler|Robamler]], so the electron when on the outer shell should take four times as long to complete a single orbit than on the inner shell?[[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 08:57, 12 August 2014 (UTC)

==Vandalism==
According to stats.grok.se, this time of year is when instances of vandalism to this article spikes.  The school year has started.[[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 16:35, 4 September 2015 (UTC)

==Assessment comment==
{{Substituted comment|length=653|lastedit=20070212143658|comment=I rated it A as it seems like a very good article (also a FAC) it is also in my opinion a topic very important within the field of physics! <span style="color:green;">'''Snailwalker {{!}}''' </span>[http://en.wikipedia.org/wiki/User_talk:Snailwalker '''talk'''] 16:10, 15 October 2006 (UTC)
* I agree. It is, strangely, a vandalism magnet, so perhaps it ought be on a few more watchlists, though. <span style="font-size: 10px">&mdash;&nbsp;[[User:Brighterorange|<span style="padding : 0px 1px 1px 1px; border : 1px solid #FFE7B0; background: #FFFFFF ; color: #FF9600">brighterorange</span>]] ([[User_talk:Brighterorange|talk]])</span> 14:36, 12 February 2007 (UTC)}}
Substituted at 08:33, 29 April 2016 (UTC)

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== Semi-protected edit request on 22 May 2019 ==

{{edit semi-protected|Atomic theory|answered=yes}}
In the philosophical atomism section, the articles does not give substantial information about the work done in India. I recommend the author to refer to the wikipedia article https://en.wikipedia.org/wiki/Kanada_(philosopher) to include some details on the work of Indian philosophers.

Here are a few lines that can be included about the work of Indian philosophers (These are words directly used from the wikipedia article).

In India, the  Vaisheshika school of philosophy founded by Kanada attempted to explain the creation and existence of the universe by proposing an atomistic theory. Kanada suggested that everything can be subdivided, but this subdivision cannot go on forever, and there must be smallest entities (parmanu) that cannot be divided, that are eternal, that aggregate in different ways to yield complex substances and bodies with unique identity, a process that involves heat, and this is the basis for all material existence. [[Special:Contributions/73.92.109.166|73.92.109.166]] ([[User talk:73.92.109.166|talk]]) 05:12, 22 May 2019 (UTC)

:If you ask me, the ''Philosphical'' section should be reduced to just three or four sentences. Dalton's scientific theory of atoms was not based on ancient philosophical theories.  Maybe he got the basic idea of the atom from the ancient Greeks, but the arguments the Greeks used to prove the existence of atoms are totally different from Dalton's, who based his arguments on experimental evidence. Thus, there is not much use in detailing how the ancients came up with the idea of atoms, beyond the need to show the disconnect with Dalton's theory. The ancient Greeks were right about atoms, but for the wrong reasons.[[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 12:24, 22 May 2019 (UTC)
:[[File:Red information icon with gradient background.svg|20px|link=|alt=]] '''Not done:''' please establish a [[Wikipedia:Consensus|consensus]] for this alteration '''[[Wikipedia:Edit requests|before]]''' using the {{tlx|edit semi-protected}} template.<!-- Template:ESp --> Another editor has disagreed with the inclusion of this. [[User:NiciVampireHeart|<b style="color:black">Nici</b>]][[User talk:NiciVampireHeart|<b style="color:purple">Vampire</b>]][[Special:Contributions/NiciVampireHeart|<b style="color:black">Heart</b>]] 19:57, 27 May 2019 (UTC)

==Rewrote lede==
{{ping|DMacks|Quondum}} I just rewrote the lede. Any thoughts? You guys seem to know your science. [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 14:36, 10 September 2020 (UTC)
:I appreciate the effort, but your rewrite doesn't work.  Dalton's atomic theory (ca. 1808) preceded the kinetic theory of gases and heat, which entered the scientific mainstream only with the work of Clausius, Maxwell, et al. (1860s).  I'll try a re-write.[[User:Ajrocke|Ajrocke]] ([[User talk:Ajrocke|talk]]) 19:19, 10 September 2020 (UTC)
::{{ping|Ajrocke}} That's fine that you sorted out the history for me, but the language of your writing is a little... purple? All I got wrong was the timing of the kinetic theory of gases. I think you made the text a little too difficult to read. I'll try to reword it into something more accessible. [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 03:23, 11 September 2020 (UTC)
::{{ping|Ajrocke}} OK, I rewrote the lede to something that is a little closer to Sesame Street level. Please have a read to make sure I haven't butchered it in the process. [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 03:38, 11 September 2020 (UTC)
:::{{ping|Kurzon}}Thanks,Kurzon, I do see merit in some of your revisions. But there are problems with some others.  "Early 1800s" is awfully vague, and it is historically incorrect to  refer to Dalton as a "scientist."  That sentence does not accurately characterize what Dalton did, for in elemental analyses as expressed in percentages by weight one sees no small integral multiples (they only appear when one holds the weight of one element constant -- see  explanation in the article below). Dalton's theory was a response to the discovery of the laws of stoichiometry, not just multiple proportions, and that has to be said in some form.  Also, the correct word must not be "substances", but rather "elements" or "chemical elements." Also, to mention the ancient tradition here is misleading, for Dalton had no sense whatever that he was continuing or reviving an ancient tradition; chemical atomism was something totally new and really quite unrelated to the philosophical tradition.  In addition, I think it's necessary to indicate that Dalton's new tradition, chemical atomism, had a lively and continuing (and absolutely vital!) development from his time to ours. One more comment: can we say that what we know now as "elementary particles" will always be thought to be indivisible? That's an absolute, abstract statement. It's better to call them what they really are thought to be by 2020 science: constituents of subatomic particles. I like your addition that the word "atom" has become an accepted convention, rather than the literal "unsplittable" idea. When I have a little time, I will offer some suggested re-writes that combine our two efforts, OK?[[User:Ajrocke|Ajrocke]] ([[User talk:Ajrocke|talk]]) 17:15, 11 September 2020 (UTC)
{{ping|Ajrocke}} When I skimmed through Dalton's ''New System of Chemical Philosophy'', I noticed that he didn't use the word "molecule".  Instead, he used the word "compound atom" and "elementary atom".  Also, he didn't realize that some elements like nitrogen (azote) exist as diatomic molecules.  I also think back then, chemists hadn't fully figured out what all the elements were.  The periodic table wasn't even invented yet.  So I went with "substances" instead of "elements", because that's probably what Dalton was thinking.

 Also, to mention the ancient tradition here is misleading, for Dalton had no sense whatever that he was continuing or reviving an ancient tradition; chemical atomism was something totally new and really quite unrelated to the philosophical tradition.

I read in a biography that it's not certain whether Dalton discovered the law of multiple proportions or whether he proposed it as a hypothesis to investigate whether atomism is correct. This implies that Dalton heard about atomism. He only needed the basic idea.  He ''did'' use the word "atom", after all.

 One more comment: can we say that what we know now as "elementary particles" will always be thought to be indivisible?

I figure that if scientists discover that certain elementary particles are in fact divisible, they will reclassify them.

 When I have a little time, I will offer some suggested re-writes that combine our two efforts, OK?

Just use an accessible writing style. Imagine you're writing this for Homer Simpson. [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 17:48, 11 September 2020 (UTC)

==The law of multiple proportions==
{{ping|Ajrocke}} How about this summary of the law of multiple proportions?  Is this more accurate?

 In the early 1800s, [[John Dalton]] compiled experimental data gathered by himself and other scientists and discovered a pattern now known as the "[[law of multiple proportions]]". He noticed that in chemical compounds which all contain a particular chemical element, the content of that element in these compounds will differ by ratios of small whole numbers.

[[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 10:43, 22 September 2020 (UTC)

== Suggestion to include some more models ==

Could we possible include the [[Cubical atom|Lewis Model]], [[Michał Gryziński|Gryziński model]], [[Hydrogen-like atom|Dirac-Gordon Equation]] and [[Vortex theory of the atom|Vortex Theory]] as further improvements in the article since they are also previously/currently suggested models? These models are mentioned in the 'Atomic Models' category box under External Links but perhaps including them in the main article would be informative. --[[User:NikeTheVictorious|NikeTheVictorious]] ([[User talk:NikeTheVictorious|talk]]) 09:04, 24 January 2022 (UTC)

== Semi-protected edit request on 27 April 2022 ==

{{edit semi-protected|Atomic theory|answered=yes}}
Change:  Solar system models proposed before Thompson always resulted in atoms spiraling into the nucleus.[28]  to  Solar system models proposed before Thompson always resulted in electrons spiraling into the nucleus.[28] [[User:KHBPGBC|KHBPGBC]] ([[User talk:KHBPGBC|talk]]) 21:34, 27 April 2022 (UTC)
: {{done}}<!-- Template:ESp -->  --[[User:Fehufanga|*Fehufangą]] ♮ [[User talk:Fehufanga|✉ Talk page]]  00:16, 28 April 2022 (UTC)

==GA Reassessment==
{{Wikipedia:Good article reassessment/Atomic theory/1}}

== Rename? ==

This is clearly a history article. Could it be renamed to '''History of atomic theory?''' [[User:ReyHahn|ReyHahn]] ([[User talk:ReyHahn|talk]]) 09:47, 27 November 2023 (UTC)
:I agree that this article has a substantial chronology of the development of this topic. However, a page called "History of atomic theory" suggests it is a sub-topic of another page called "Atomic theory", where that main-topic page has substantial content on aspects beyond the history. Otherwise, the title is needlessly verbose (and says it would ''only'' cover historical development). What would be the remaining atomic-theory page once the history as you see it is offloaded? See [[WP:TITLE]] and [[WP:Splitting]] for the relevant guidelines. [[User:DMacks|DMacks]] ([[User talk:DMacks|talk]]) 10:13, 27 November 2023 (UTC)
::I understand that we do not have an atomic theory article so it seems like extra work (thought it is unnecessary to have such an article as we have articles for quantum chemistry, [[hydrogen atom]], quantum mechanics, [[Atomic, molecular, and optical physics]], and just [[atom]]). However, I would insist to move it in the sense that it is at odds with other history articles which are usually called "history of" and do not have necesssarily a corresponding article. See for example [[History of molecular theory]] or [[History of subatomic physics]].--[[User:ReyHahn|ReyHahn]] ([[User talk:ReyHahn|talk]]) 10:17, 28 November 2023 (UTC)
:'''Rename''' I think you should make this the "history" page for the [[Atom]] article and cut back some of the content in that article now under 'history of atomic theory'. You could call is "History of the Atom" I suppose. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 16:24, 26 January 2024 (UTC)
:Hah, there is also [[Atomism]], yet another redundant history. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 22:29, 11 February 2024 (UTC)
{{ping|Kurzon}} great work with the article. Would you care to comment on the name of the article? Do you have a preference?--[[User:ReyHahn|ReyHahn]] ([[User talk:ReyHahn|talk]]) 13:47, 1 February 2024 (UTC)
::'''Oppose''' "History of the atom". Atoms existed long before atomic theory, and the article should cover the history of the latter, not the history of the former. I am only mildly opposed to "History of atomic theory". Not every article on a historical scientific topic starts with "History of". We don't have [[History of aether theories]], but rather [[Aether theories]]. As currently constructed, [[Atomic theory]] is the historical background to [[Atomic physics]]. We could have an article called [[History of atomic physics]], but [[Atomic theory]] is a better name for that article. --[[User:Srleffler|Srleffler]] ([[User talk:Srleffler|talk]]) 07:02, 4 February 2024 (UTC)
:::To be clear, you are ok with '''Rename''' "History of atomic theory" correct? [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 16:42, 4 February 2024 (UTC)
::::As stated, I am mildly opposed to "History of atomic theory". I am not convinced that the proposed renaming is necessary.--[[User:Srleffler|Srleffler]] ([[User talk:Srleffler|talk]]) 05:18, 6 February 2024 (UTC)
:::History of atomic physics would be ok by me and match [[Atomic physics]]. We could build up the non-history content on atoms there. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 17:02, 4 February 2024 (UTC)

:I have no objection to renaming this article to "History of atomic theory". It makes no difference to me. [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 13:57, 1 February 2024 (UTC)

== Pauli principle ==

Atomic theory in the quantum era makes no sense without a discussion of the Pauli principle. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 17:44, 1 February 2024 (UTC)

:Be my guest. [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 22:47, 1 February 2024 (UTC)
:{{done}} [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 21:05, 2 February 2024 (UTC)

== Uncertainty principle ==

I deleted a paragraph on the uncertainty principle (again). I suppose there are a few connections between atomic theory and uncertainty principle, but if these are notable in the context of the article they should be called out (with refs). Almost all of these connections are just tidbits not really physics. Of course the principle applies but it's not useful for understanding atoms. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 21:05, 2 February 2024 (UTC)

==Physical and chemical atoms per Dumas==
Jean-Baptiste Dumas defined a "physical atom" as a particle that cannot be divided by "physical forces" such as temperature and pressure and a "chemical atom" as a particle that cannot be divided by chemical reactions. Hydrogen gas particles are physical atoms but not chemical atoms because if you mix hydrogen gas and chlorine gas, their molecules split so that their atoms can combine into hydrogen chloride (HCl).

By this description, I suppose that hydrogen chloride molecules would be "chemical atoms" but not "physical atoms" because the only way to separate the hydrogen from the chlorine is electrolysis, a physical process.  Remember that this is all from the perspective of early 19th century chemists.  What I'm looking for is a source that confirms my supposition.  For the paragraph above, I already have a source, but that book doesn't mention electrolysis. [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 17:17, 4 February 2024 (UTC)

:I would not assume electrolysis, esp. in the early 19th century. Water soluble HCl is chemically reactive in many ways. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 19:10, 4 February 2024 (UTC)

==Stanislao Cannizzaro==
Cannizzaro championed the modern definitions of atom and molecule. What were some of his arguments for it?  I have a hunch it had something to do with bonding.  Molecular bonds and atomic bonds work very differently. [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 17:39, 4 February 2024 (UTC)

:I suppose you could call delocalized bonding like benzene as "molecular", but Cannizzaro was long before "bonding" was even known. Cannizzaro was an advocate of Avogadro's law and of moving to a consistent nomenclature. At that time, molecules and atoms were not really known.  He argued that the smallest isolatable unit is molecule and that "molecules" are composed of smaller chemically indestructible units to be called atoms. Bonding was far in the future. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 18:51, 4 February 2024 (UTC)
::You seem to know a lot about this. Why am I the only one working on this article? I am just working off what I remember from high school. [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 20:59, 4 February 2024 (UTC)
:::Everything I know about Cannizzaro came from reading the Pullman reference. 
:::I do plan to contribute to this article in future. I'm working on [[Spin (physics)]] just now. Thanks to your efforts this article is in better shape than many. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 23:20, 4 February 2024 (UTC)
:I only know Cannizzaro from working on the [[Karlsruhe Congress]]. He was the protagonist and the congress lead to the standarization of atomic weights. He basically did so by employing [[Avogadro's law]] to show that common gases (hydrogen, oxygen) were made from composite molecules and not atoms.--[[User:ReyHahn|ReyHahn]] ([[User talk:ReyHahn|talk]]) 00:50, 5 February 2024 (UTC)
::Didn't Avogadro himself show that hydrogen and oxygen molecules are diatomic? [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 01:17, 5 February 2024 (UTC)
:::I thought Avogadro just did the theory but maybe I am wrong. There were still experimental discrepancies anyway and Cannizzaro solved them.--[[User:ReyHahn|ReyHahn]] ([[User talk:ReyHahn|talk]]) 01:34, 5 February 2024 (UTC)
::::I just reread his 1811 paper. Yeah, he figured that oxygen gas particles are diatomic. He measured oxygen's atomic weight to be 15.074. [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 02:39, 5 February 2024 (UTC)
:::::Good to know. I guess [[Amadeo Avogadro]] page needs work too. If I have the time I will reread on the Congress to see what were the experimental discrepancies.--[[User:ReyHahn|ReyHahn]] ([[User talk:ReyHahn|talk]]) 08:24, 5 February 2024 (UTC)

https://archive.org/details/sketchofcourseof00cannrich/page/4/mode/2up?q=Berzelius

Reading pages 2 to 4, as I understand, Berzelius could not fathom that some elemental gases like nitrogen exist in diatomic molecules that can split.  Eg A litre of nitrogen gas and a litre of oxygen can react to form two litres of nitric oxide. Berzelius thought the reaction was N + O → NO when in fact it is N<sub>2</sub> + O<sub>2</sub> → 2NO.  Berzelius called particles of nitrogen gas "elementary atoms", which imply they're indivisible, they can't be split into smaller nitrogen particles.  Pullman (1998) on page 202 says that Berzelius overused the word atom.  So if Berzelius used the word "atom" and "molecule" in the way we do, it might have occurred to him that particles of nitrogen gas could be diatomic.  Am I correct? [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 16:17, 5 February 2024 (UTC)

:You may well be correct, but we can't know what "might have occurred". I think your next post is a better strategy: you quote Cannizzaro explaining how Berzelius' model incorrectly handles hydrogen compounds he says outright that the atomic models of Avogadro and Ampere work better. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 16:54, 11 February 2024 (UTC)

{{ping|Johnjbarton|ReyHahn}} This passage comes from Cannizzaro's book:

{{blockquote|I then show how Berzelius, being unable to escape from his own dualistic ideas, and yet wishing to explain the simple relations discovered by Gay-Lussac between the volumes of gaseous compounds and their gaseous components, was led to formulate a hypothesis very different from that of Avogadro and of Ampere, namely, that equal volumes of simple substances in the gaseous state contain the same number of atoms, which in combination unite intact ; how, later, the vapour densities of many simple substances having been determined, he had to restrict this hypothesis by saying that only simple substances which are permanent gases obey this law ; how, not believing that composite atoms even of the same order could be equidistant in the gaseous state under the same conditions, he was led to suppose that in the molecules of hydrochloric, hydriodic, and hydrobromic acids, and in those of water and sulphuretted hydrogen, there was contained the same quantity of hydrogen, '''although the different behaviour of these compounds confirmed the deductions from the hypothesis of Avogadro and of Ampere.'''

I conclude this lecture by showing that we have only to distinguish atoms from molecules in order to reconcile all the experimental results known to Berzelius, and have no need to assume any difference in constitution between permanent and coercible, or between simple and compound gases, in contradiction to the physical properties of all elastic fluids.}}

What exactly was Cannizzaro talking about in the part I bolded? [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 03:56, 11 February 2024 (UTC)

:I believe he is saying that Berzelius' model would predict that the acids (HCl, HI, HBr) would have the same quantity of hydrogen as water and sulphuretted hydrogen (H20 and H2S).  At the time of course they had no forumla, just a large collection of (sometimes incorrect or confusing) experimental observations. (I have a vivid memory of a college chem lab where we prepared some simple compound and analyzed its atomic formula. Everyone struggled to and fudged their numbers to get 2:1, but then the Prof. said anyone with 2:1 gets -10 points: the reaction can't give exactly 2:1!). [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 16:48, 11 February 2024 (UTC)
::No, I suspect it's something else. Too bad we don't have his lecture transcripts. [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 01:45, 12 February 2024 (UTC)


== Requested move 21 February 2024 ==
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<small>'''{{smallcaps|result:}}'''</small><br />'''[[Wikipedia:Requested moves/Closing instructions#Three possible outcomes|Moved]]''' per consensus seen below. Thanks and kudos to editors for your input; everyone [[User:Paine Ellsworth/Clickable button – Publish buttons|stay&nbsp;healthy]]''!'' '''''[[User:Paine Ellsworth|<span style="font-size:92%;color:darkblue;font-family:Segoe Script">P.I.&nbsp;Ellsworth</span>]]'''''&thinsp;,&nbsp;[[Editor|<span style="color:black">ed.</span>]]&nbsp;[[User talk:Paine Ellsworth|<sup>put'er&nbsp;there</sup>]]&nbsp;<small>04:24, 23 March 2024 (UTC)</small><br /><small>As an aside, I misread that very last sentence and I fell on the floor LOL''!'' I read "It would look like ''an'' atom." HA''!'' well, maybe you had to be there. '''''[[User:Paine Ellsworth|<span style="font-size:92%;color:darkblue;font-family:Segoe Script">P.I.&nbsp;Ellsworth</span>]]'''''&thinsp;,&nbsp;[[Editor|<span style="color:black">ed.</span>]]&nbsp;[[User talk:Paine Ellsworth|<sup>put'er&nbsp;there</sup>]]&nbsp;<small>04:29, 23 March 2024 (UTC)</small></small>
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[[:Atomic theory]] → {{no redirect|History of atomic theory}} – An atomic theory article would be to vast and articles for [[quantum chemistry]], [[hydrogen atom]], [[quantum mechanics]], [[Atomic, molecular, and optical physics]], and just [[atom]], exist already. This page as it currently stands it is a history article, most of the section headers could be promoted to level 1 headers if the article name is changed. This move is also in line with other "history of" articles that do not necessarily have a main article. See for example [[History of molecular theory]] or [[History of subatomic physics]]. [[User:ReyHahn|ReyHahn]] ([[User talk:ReyHahn|talk]]) 10:42, 21 February 2024 (UTC)

Other possibilities include [[History of the atom]] (current redirect here) or [[History of atoms]].--[[User:ReyHahn|ReyHahn]] ([[User talk:ReyHahn|talk]]) 10:43, 21 February 2024 (UTC)

{{Ping|Johnjbarton|Srleffler|Kurzon|DMacks|asilvering}} pinging previous users that have showed interest/objections to this move. Please be free to just copy your previous comment in you prefer.--[[User:ReyHahn|ReyHahn]] ([[User talk:ReyHahn|talk]]) 10:47, 21 February 2024 (UTC)

:'''Strongly Agree''' Title should match content. The subject notable and needed. Purpose of other articles will be clearer once this one is not overlapping their names. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 16:01, 21 February 2024 (UTC)
:<s>'''Rename per nom'''. Hard to disagree when the article title is "Atomic theory" and all the content is under the heading "History".</s> [[User:Jähmefyysikko|Jähmefyysikko]] ([[User talk:Jähmefyysikko|talk]]) 16:34, 21 February 2024 (UTC)
:'''Comment''': Since you're asking for a no-redirect move, would you want [[Atomic theory]] to redirect instead to [[Atom]]? -- [[User:Asilvering|asilvering]] ([[User talk:Asilvering|talk]]) 18:39, 21 February 2024 (UTC)
::The problem is that "atomic theory" is barely a term now, but I have no problem making [[atomic theory]] a redirect to [[atom]].--[[User:ReyHahn|ReyHahn]] ([[User talk:ReyHahn|talk]]) 09:13, 22 February 2024 (UTC)
:::Looking at [[Special:WhatLinksHere/Atomic_theory]], it seems that most of the links are in the historic context, and it seems reasonable to keep [[Atomic theory]] pointing here. A few of the links should perhaps be retargeted to [[Atomic physics]] or [[Atom]]. [[User:Jähmefyysikko|Jähmefyysikko]] ([[User talk:Jähmefyysikko|talk]]) 10:04, 22 February 2024 (UTC)
:'''No objections''' [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 09:07, 22 February 2024 (UTC)
*'''Support''' per above. Note that hundreds of pages link to [[Atomic theory]] and that title should redirect to this article for the mean time.  &#8213; [[User:Synpath|'''Syn''']][[User talk:Synpath|path]] 18:07, 22 February 2024 (UTC)
*I'm not sure "history of atomic theory" is clear. This article does not overlap with [[Atomism]], as I would expect a history article to. [[User:Srnec|Srnec]] ([[User talk:Srnec|talk]]) 21:27, 22 February 2024 (UTC)
*:@[[User:Srnec|Srnec]] Please check. The entire last part of [[Atomism]] is a summary of [[Atomic theory]]
*:* Modern atomic theory  ... Main article: Atomic theory
*:With this proposal, the [[Atomism]] history would be
*:* Modern atomic theory  ... Main article: History of atomic theory
*:And the first part of this article is a summary of [[Atomism]].
*:Seems to me it fits perfectly after the rename. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 23:03, 22 February 2024 (UTC)
*::To me, at least, "atomic theory" is actually clearer than "history of atomic theory", since I default to assuming that "atomic ''theory''" means modern scientific atomism. But when you put "history" on the front that assumption goes out the window and I assume that, like [[History of evolutionary thought]], it runs the gamut from antiquity to the present. ''That'' article, however, is, at [[Atomism]]. —[[User:Srnec|Srnec]] ([[User talk:Srnec|talk]]) 00:29, 23 February 2024 (UTC)
*:::First, "atomic theory" is not in my view "modern scientific atomism". Atomism was a collection of philosophical and pre-scientific discussions that got lucky. Lots of such discussions where made, say "angels" or "aether" but they failed. Only luck confers upon Atomism a particular excellence. There is no such thing as "scientific atomism".
*:::Atomic theory is a consequence of the scientific method and this article describes its history. The article would be complete and correct without mentioning "atomism" beyond placing some ideas in play. 
*:::Second, if you believe that this article is "modern scientific atomism" why don't we merge it with "atomism"? (My answer would be simple, it's not modern atomism so merging makes no sense.) 
*:::Third, when I click on [[Molecular orbital theory]] I expect an article about a "theory". Similarly [[Cell theory]], [[density functional theory]] and so on. But when I click on [[atomic theory]] I get "history of atomic theory". I have to read the fine print in this article to realize that the wikipedia article about atomic theory is in [[Atomic physics]]. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 01:48, 23 February 2024 (UTC)
*'''Oppose''' per Srnec. Atomic theory is clearer and more succinct. &#32;<span style="font-variant:small-caps; whitespace:nowrap;">[[User:Headbomb|Headbomb]] {[[User talk:Headbomb|t]] · [[Special:Contributions/Headbomb|c]] · [[WP:PHYS|p]] · [[WP:WBOOKS|b]]}</span> 01:18, 23 February 2024 (UTC)
*:I'm still struggling to understand this point of view. I gather that you view "Atomic theory" as identical with "History of Atomic Theory", so the prefix "History of" is not needed. I assume then that you would agree to: 
*:# Remove the "History" layer of the TOC here since it is not needed (as we would in an article called "History of"). The entire TOC is under History here, so the article looks silly now.
*:# Change the lede to identify the topic as history, eg: "'''Atomic theory''' is history of the scientific theory that matter is composed of particles called atoms." or something like that. I think this is awkward and I don't think any source supports it, but it would reflect the content of the article.
*:[[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 18:35, 26 February 2024 (UTC)

:'''Strongly Agree''' This article covers the history, not the theory itself. [[User:TheBooker66|TheBooker66]] ([[User talk:TheBooker66|talk]]) 10:06, 19 March 2024 (UTC)
*'''Oppose'''  I think the following point has been made above, but let me elaborate: It is true that the article covers the history of the atomic theory, but what would an article on "the theory itself" even look like, if it were not organized historically?  In a strong sense, an encyclopedia article on "the atomic theory" has much in common with an encyclopedia article on "the caloric theory" or "the phlogiston theory"; we don't want to entitle these articles "history of the caloric theory" and "history of the phlogiston theory" -- we don't, because they are intrinsically historical subjects -- and we shouldn't do that to the atomic theory, either.  To be sure, we no longer think that the caloric theory and the phlogiston theory are true pictures of nature, but we also don't think of "atoms" in the original (and etymological) sense of ultimate particles of nature.  What we call atoms today no longer reside in the realm of theory, and they are not ultimate particles.  The "atomic theory" is an intrinsically historical subject; changing the name of the article to "history of" simply adds unnecessary verbiage.  By the way, I am a professional academic historian of science, with a specialty in the history of chemistry (I have written widely on the subject of this article), so I have some standing to express an opinion here.[[User:Ajrocke|Ajrocke]] ([[User talk:Ajrocke|talk]]) 18:43, 19 March 2024 (UTC)
*:Ooh, a professional! I do good on this article? [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 19:18, 19 March 2024 (UTC)
*:* ' but what would an article on "the theory itself" even look like,' 
*:It would look like [[Atom]]. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 21:13, 19 March 2024 (UTC)
<div style="padding-left: 1.6em; font-style: italic; border-top: 1px solid #a2a9b1; margin: 0.5em 0; padding-top: 0.5em">The discussion above is closed. <b style="color: #FF0000;">Please do not modify it.</b> Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.</div><!-- from [[Template:Archive bottom]] -->
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== Maxwell's early evidence of atoms ==

While reading on another topic I came upon
* J. C. Maxwell, A Treatise on Electricity and Magnetism (reprinted New York, 1954), vol. 2,
274-6
Here Maxwell argues that magnetic fields can always be reproduced by many tiny electrical currents but never the reverse. To unify the model of cause of electromagnetism (as evident in his equations), one must use tiny electric currents to explain magnets.  He says ''
* "We must now regard a magnet as containing a finite, though very great, number of electric circuits, so that it has essentially a molecular, as distinguished from a continuous, structure."''
(Molecular was a term for atomic at one point).
Thus Maxwell provided evidence for atoms as the origin of magnetism in 1873.

In 1892 Lorentz published an atomic model of Maxwell's equations.
* {{Cite book|last=Pais|first=Abraham|year=1986|location=New York|title=Inward Bound: Of Matter and Forces in the Physical World|publisher=Oxford University Press|isbn=978-0-19-851971-3|pages=[https://archive.org/details/inwardboundofmat00pais_0/page/228 228–230]|url=https://archive.org/details/inwardboundofmat00pais_0/page/228}}
* https://www.scientificamerican.com/article/happy-birthday-electron/

Both of these imply "electrons" in some sense. So I think "Atoms were thought to be the smallest possible division of matter until 1897" isn't quite correct. As is usually the case, Thomson did not so much "discover" the electron, as provide the definitive experimental evidence for an idea that was all around. Lorentz intepreted Zeeman's results in 1896 as the result of a bound charged particle in an atom and giving an e/m value. (Pais, pg 10). What Thomson really did in 1897 was measure e/m for cathode rays and then push on to measure e and m separately in 1899; that combination is what gave him the title for the "discovery".

Now I do not think we should to into all of this depth in this article. But we also should not perpetuate the "until 1897" demarcation. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 00:44, 20 March 2024 (UTC)

:If Maxwell hypothesized the electron, where did he think the electrons come from?  Thomson said that electrons are embedded in atoms, and in an electric current they detach and pass to an adjacent atom. THAT is what he discovered: that atoms are divisible. [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 12:42, 20 March 2024 (UTC)
::Sorry if I was not clear. It was Lorentz that hypothesized the electron. Maxwell provided evidence for atoms which may create currents for magnetism. 
::I doubt your claim because I believe important Thomson's contribution was experimental. His conjectures were similar to many others and some of what he said later did not turn out. When we look back at what he wrote we focus on the things that match current understanding. That's why experiments are so important: when reproduced they have meaning. (Almost all discoveries of particles were experiments done based on existing theory that hypothesized particles).
::But if you are 100% correct that's great! However, the article does not reflect this. In particular the article cites Thomson's own work for the "Atoms were thought to be the smallest possible division of matter until 1897" contrary to [[WP:PSTS]]. I suppose I should have just said that from the outset. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 16:03, 20 March 2024 (UTC)
:::Well, I suppose we could split hairs on this.  I did use the word "thought". Most everyone ''thought'' that atoms were indivisible until Thomson ''proved'' otherwise. Even if they heard of Maxwell's hypothesis they probably didn't take it seriously until Thomson provided proof and well as details Maxwell didn't conceive. [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 17:05, 20 March 2024 (UTC)
== Relativistic atom ==

Would a comment on [[Walter Gordon (physicist)]] on solving the relativistic equation ([[Dirac equation]]) for the hydrogen atom be of interest here? What about the [[Lamb shift]]? Or are these ideas heavily focused on hydrogen? [[User:ReyHahn|ReyHahn]] ([[User talk:ReyHahn|talk]]) 12:20, 23 March 2024 (UTC)

:Hydrogen is simply the iconic atom. Both issues are related to atomic theory IMO. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 17:43, 23 March 2024 (UTC)
== Energetics ==

Maybe a mention to [[energeticism|Ostwald's energetics]] could fit in the statistical mechanics section. [[User:ReyHahn|ReyHahn]] ([[User talk:ReyHahn|talk]]) 09:36, 19 April 2024 (UTC)
==Mass of an electron==
{{ping|Johnjbarton}} The article says that Thomson measured the mass of an electron to be 1/8000 of a proton.  But I looked through Thomson's paper and he didn't measure the mass, but the mass-to-charge ratio.  When was the mass measured?  Was it Milikan's oil drop experiment?  If you measure the charge of an electron and you already know the mass-to-charge ratio, you can then calculate the mass. [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 12:00, 14 May 2024 (UTC)

:I didn't find 8000, but I did edit the m/e section for the electron based on Whittaker. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 18:17, 14 May 2024 (UTC)

{{reply to|Johnjbarton}} In his 1899 paper, Thomson writes: "This mass is exceedingly small, being only about 1.4 × 10<sup>-3</sup> of that of the hydrogen ion". Does that mean the electron is 1,400 time smaller than hydrogen, or 1/0.0014 times smaller? [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 18:35, 14 May 2024 (UTC)

:"being only about" 1.4 times 1/1000 times hydrogen ion. So 700 times less massive, my mistake. (and it's not smaller but lighter) [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 18:43, 14 May 2024 (UTC)

{{ping|Johnjbarton|Ajrocke}} How did Thomson know the charge on a hydrogen ion is equal to the charge on an electron? Which papers did he lay out his proof? [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 09:21, 15 May 2024 (UTC)
:Doesn't this follow from charge neutrality? The hydrogen atom is neutral.--[[User:ReyHahn|ReyHahn]] ([[User talk:ReyHahn|talk]]) 09:29, 15 May 2024 (UTC)
:Thomson measured e for ions and for photo-electrons. He measured m/e for cathode rays and photo-electrons. In his photoelectron paper he says
:* W. Wien (Wied. Ann. lxv. p.440) and Ewers (Wied. Ann. lxix. p.187) have measured the ratio of m / e for the positive ions in such a tube, and found that it is of the same order as the value of m / e in ordinary electrolysis; Ewers has shown that it depends on the metal of which the cathode is made. Thus the carriers of positive electricity at low pressures seem to be ordinary molecules, while the carriers of negative electricity are very much smaller.
:[[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 22:04, 15 May 2024 (UTC)

Well I don't think at the time Thomson knew that a hydrogen atom had just one electron. [[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 09:59, 15 May 2024 (UTC)

==Multiplier/multiples==
{{ping|Johnjbarton}} Let's revisit this issue.

{{quote|In an April 1911 paper, Ernest Rutherford estimated that the charge of an atomic nucleus, expressed as a multiplier of hydrogen's nuclear charge (e), is roughly half the atom's atomic weight, based on how various types of metal foil scattered alpha particles.}}

I think it should be "multiplier".[[User:Kurzon|Kurzon]] ([[User talk:Kurzon|talk]]) 18:30, 18 May 2024 (UTC)

:? I guess this is a quote from somewhere.  But it is unrelated to the discussion on [[Rutherford scattering experiments]]. In the quote above "multiplier" seems fine to me. The other sentence was different and anyway I removed it for other reasons. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 19:06, 18 May 2024 (UTC)
== Rutherford's model is sometimes called the "planetary model" ==

The article says;
* Rutherford's model is sometimes called the "planetary model".
With a ref to 
* {{cite web |title=Rutherford model {{!}} Definition & Facts |url=https://www.britannica.com/science/Rutherford-model |website=Encyclopedia Britannica |access-date=23 August 2021 |language=en}}
While working on [[Rutherford atom]] I looked into many references discussing planetary models. Planetary models appeared before 1911, Rutherford's model was not planetary (he made no comment on the electrons), and the concept of associating planetary models with atom appeared long after 1911, in association with Bohr's model of circular orbits. Please see [[Bohr_model#Symbolism_of_planetary_atomic_models]] and the ref below.

The Britannia site has other errors, eg "Physicist Ernest Rutherford envisioned the atom as a miniature solar system,". A comprehensive history says "Rutherford did not specify the electronic arrangement..." {{Cite journal |last=Heilbron |first=John L. |date=1968 |title=The Scattering of α and β Particles and Rutherford's Atom |url=https://www.jstor.org/stable/41133273 |journal=Archive for History of Exact Sciences |volume=4 |issue=4 |pages=247–307 |doi=10.1007/BF00411591 |jstor=41133273 |issn=0003-9519}}

I think this sentence should be removed despite the reference. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 23:11, 23 October 2024 (UTC)
:I checked the [[plum pudding model]] for consistency, and its cited content agrees that while Rutherford's model was a dense positive center and electrons around it, it did not have any specific structure to the electron pool or its motion. [[User:DMacks|DMacks]] ([[User talk:DMacks|talk]]) 23:40, 23 October 2024 (UTC)
== GA concerns ==

I am concerned that this article no longer meets the [[WP:GA?|good article criteria]] because there are uncited statements throughout the article, including entire paragraphs. Is anyone interested in fixing up this article? [[User:Z1720|Z1720]] ([[User talk:Z1720|talk]]) 20:53, 5 October 2024 (UTC)

:The other issue here is a large proportion of primary refs. I have this article on my todo list. I'm familiar with the sources from Thomson on. I'm currently working on [[Bohr model]].
:If you or anyone else added citation-needed tags I would fix them. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 22:10, 5 October 2024 (UTC)
::{{ping|Johnjbarton}} Sorry for not responding sooner: I added cn tags to the article per your request above. [[User:Z1720|Z1720]] ([[User talk:Z1720|talk]]) 02:12, 27 October 2024 (UTC)
:::Excellent thanks! [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 02:17, 27 October 2024 (UTC)
== Highlighting atomic models ==

I think we should alter the table of contents and add a bit of content to highlight models of the atom consistent with the title. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 17:35, 30 October 2024 (UTC)