Wikipedia:Peer review/Atom/archive2

Atom

Previous peer review

This peer review discussion has been closed.
Dear Peer Reviewer,

Over the past few months this article has undergone significant expansion and, hopefully, improvement. I believe it has become a reasonably comprehensive, high-level summary on the topic of atoms. The article is still in need of references in a few sections and I am working to address that concern. My hope is that lay readers will find this an approachable article on the topic that doesn't require a degree in physics. It would be greatly appreciated if you could spend a few minutes reviewing the article and seeing what needs to be improved. I'm especially interested in knowing about parts of the article that may need a better explanation, as well as any other topics you believe should be covered. (Note that the article does not cover the topic of elements in great detail, as these are the focus of the chemical element article.)

Thank you!—RJH (talk) 20:07, 9 January 2008 (UTC)

Comments by Seegoon

Fortunately for you, I redefine lay. I'm beyond lay. Hopefully I'll understand some of this.

• It's not immediately apparent what the black bar in the infobox illustration represents.
  • I think that's supposed to be a unit scale of 1 Angstrom. I added an explanation to the caption.—RJH (talk)
• Just finished the lead, it all made sense to me. The only part I didn't like was how "In 1897 J. J. Thomson discovered that the atom contained charged particles called electrons. Ernest Rutherford then showed that most of an atom's mass, and its positive charge, were located at the core." didn't flow from one sentence to the next particularly smoothly, but that's just my reading/writing style there. revised Furmanj (talk) 13:50, 11 January 2008 (UTC)
• Consider Wiktionary-linking "discrete" - there's room for confusion there.
  • Okay, I added a transwiki-link.—RJH (talk) 18:19, 11 January 2008 (UTC)
• In the second last paragraph of history, you wikilink isotope twice. revised Furmanj (talk) 13:50, 11 January 2008 (UTC)
• I think the book cited in "General references" should be done using {{citebook}}.
  • Will do.—RJH (talk) 18:19, 11 January 2008 (UTC)

OK - I finished it. I wouldn't say I understood it all, but I comprehened all the prose, so it's clearly well written. Sorry I can't really help. Seegoon (talk) 21:26, 10 January 2008 (UTC)

Thank you for taking a look through the article and inserting fixes.—RJH (talk) 18:19, 11 January 2008 (UTC)

• A script has been used to generate a semi-automated review of the article for issues relating to grammar and house style. If you would find such a review helpful, please click here. Thanks, APR _t 06:35, 14 January 2008 (UTC)

some suggestions

• "An atom is electrically neutral if it has the same number of protons as electrons" atom by definition is neutral, so it has to have the same number of electrons and protons
  • Do you not consider an ionized atom to be an atom?
    • Atoms are normally assumed to be electrically neutral, but I think that saying "ionized atoms are not atoms" is taking it a bit too far. That said, IUPAC's gold book defines atom as having Z protons and Z electrons,[1]. IMO, our article will be clearer if we emphasize that atoms can be charged when the number of electrons is not Z, although in that case they are more specifically referred to as ions. --Itub (talk) 18:01, 17 January 2008 (UTC)
• introduction might be slightly long, verbose. I personally prefer more succint information in the intro, but it is just a personal preference.
  • Sorry if the lead seems too long for you. It was put together so as to satisfy the guidelines at Wikipedia:Lead_section. In particular that it "be capable of standing alone as a concise overview of the article". Anyway I tried to tighten it up a little.—RJH (talk)
• in infobox: switch from mass to mass range; maybe for charge, besides zero add in paranthesis neutral
• the infobox 'feels' like a stub (I am not sure what else you could add in though)
  • I added in a "Components" section.—RJH (talk)
• maybe add something about the more general 'stability of an atom'. you wrote about the nucleus, but what about electrons? (i.e. cations and ionization potentials?)
  • The last paragraph of "Electron cloud" covers ionization in brief. I added a mention of ionization potential.—RJH (talk)
• I didn't see anthing about unstable, low neutron-nucleii absorbing inner shell electrons (the idea of internal reaction)
  • It's mentioned on the radioactive decay page as a form of beta decay.—RJH (talk)
• possibly add something about rare gases since they exhibit macromolecular interactions of ~free atoms
• in the nucleosynthesis you talk about the big bang period. but what about later nucleosyntheses? (i.e. stars burn everything till 56Fe, and all elements above that appear in supernova explosion)
  • This is mentioned in the first paragraph, last sentence of the Nucleosynthesis section.—RJH (talk)
• this could be related more to the notion of element, but what about distribution of atoms in universe? (most of the universe is still as hydrogen and helium)
  • You probably mean abundances. This is covered on the chemical element page.—RJH (talk)
• in history section maybe add discoveries of particles that hold nucleii together
  • Okay, I'll see what I can dig up.—RJH (talk)
• there is nothing specific enough about the number of neutrons relative to the number of protons that are found in known nucleii.there is just the image that shows that is beter to have slightly more neutrons than protons. anybody knows why is that? also is there a good correlation between the number of neutrons and protons in the most stable isotopes that describes that figure?
  • I added an explanatory paragraph to the Nucleus section. Hopefully it makes sense.—RJH (talk)

all these points are suggestions that you may want to incorporate them into the article if you find adequate to the topic. hope it helped Nergaal (talk) 10:26, 16 January 2008 (UTC)

Thank you for your feedback. I'll try to incorporate your suggestions.—RJH (talk) 17:26, 17 January 2008 (UTC)

Comments by Itub

• The reference to http://www.commonsensescience.org/atom_models.html looks fishy. I wouldn't cite someone who discusses the "Lucas model" (which seems to be an "alternative" theory unknown by the scientific literature) and the Bible together with the real models of the atom (not to mention that there are some inaccuracies in the discussion of the real models as well). --Itub (talk) 11:12, 16 January 2008 (UTC)
  • I've replaced that citation with a couple of others.—RJH (talk)

• Did Robert Brown really name his discovery Brownian motion? I think it is more likely that someone else started naming it that way. --Itub (talk) 11:26, 16 January 2008 (UTC)
  • I suspect probably not, although one source said he did. The text has been modified.—RJH (talk)

• The statement that "Thomson created a technique for separating different types of atoms through his work on ionized gases, which subsequently led to the discovery of isotopes" may be an oversimplification. The concept of isotope is generally attributed to Soddy, who got the Nobel Prize in 1921 for it, and the isotopes in question were found through chemical analysis of radioactive decay products. Thomson's method did contribute to discovering isotopes in other elements, such as neon. --Itub (talk) 13:39, 16 January 2008 (UTC)
  • I'll work on fixing that. Thank you for the feedback.—RJH (talk) 17:40, 18 January 2008 (UTC)

Comments from Awadewit

I'm approaching this article from a layperson's perspective. I have no science training, but I am interested in science and I like to read popular science books for fun. So here are my suggestions - take them for what they are worth:

• Infobox: Unit "fm" is not linked or explained
  • I added a comparison.

• In chemistry and physics, an atom (Greek ἄτομος or átomos meaning "the smallest indivisible particle of matter, i.e. something that cannot be divided") is the smallest particle characterizing a chemical element. - Why "in chemistry and physics"? It seems to me like a whole host of fields like molecular biology could be added on here. Are they really necessary to the definition?
  • I think it was written to distinguish the physics concept from others covered on the disambiguation page. But it probably isn't necessary.—RJH (talk)

• The total protons in an atom define the chemical element to which it belongs, while the number of neutrons determines the isotope of the element. - "An atom is classified according to its protons and neutrons: the number of protons determines the chemical element and the number of neutrons determines the isotope of that element." - Is a formulation like this clearer?
  • Changed to suggested text.

• The concept of the atom as an indivisible component of matter was proposed by early Indian and Greek philosophers. - "first proposed"?
  • Okay; probably the first written proposal.

• Early chemists provided a physical basis for this idea by showing that certain substances could not be further broken down by chemical methods. - A century would be helpful for readers unfamiliar with scientific history
  • Done.

• The electrons determine the chemical properties of an element, and strongly influence an atom's magnetic moment. - This was the only thing that was unfamiliar to me in the lead. I didn't know what a "magnetic moment" was. I clicked on it, but the lead of that article is not that helpful for someone like me.
  • I changed it to "magnetic properties".

• The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny or small quantities has been around for thousands of years - Why both "tiny" and "small"?
  • Fixed.

• In the "History" section, many scientists are introduced by name only. It is helpful to readers to give a little phrase introducing them. Let readers know what Boyle, Lavoisier, and others are known for in the history of science. It helps provide some context.
  • Okay. I was trying to keep it summary style without delving into too many details. It could easily become a book.

• In the "History" section there is a big leap from Democritus to Boyle. This 2000-year gap needs to be filled in or explained to the reader.
  • Explained.

• The paragraph on Brownian motion needs to be made clearer, I think. It is my understanding that Brownian motion helps to prove the atomic theory because the motions of the particles demonstrate that they are being hit by "atomic"-like structures. I don't think this comes across very well in this paragraph to someone who doesn't already know it.
  • I hope it's a little clearer now.

• What do you think about explaining the gold foil experiment a bit? It is an easy one to explain and draw an image for and there are great Rutherford quotes about it (cannon ball and cloud) that really illustrate the atom clearly for the uninitiated. It would help "humanize" the page (horror of horrors, I know).
  • Okay it's expanded.

• For someone who doesn't already know what an isotope is, I don't think that the isotope paragraph in "History" explains the concept well. It is confusing because it seems to suggest that there are multiple types of hydrogen, for example, actually on the periodic table.
  • Tried to clarify without becoming too redundant.

• The development of the mass spectrometer allowed the exact mass of atoms to be measured. - You should probably explain what a mass spectrometer is in a phrase or a sentence.
  • Done.

• Francis William Aston used this technique to demonstrate that isotopes had different masses. - "technique" or "instrument"? The previous sentence said "spectrometer", not "spectroscopy".
  • Fixed.

• The "History" section feels disconnected - the paragraphs do not flow into one another.
  • I tried to address this.

• What do you think about a timeline that could be linked to the "History" section?
  • Probably not a bad idea.

• The paragraph on quarks, bosons, etc. explains very little to someone who doesn't know these terms and concepts or isn't willing to click on each one. I wonder if it is possible to expand a bit here?
  • I attempted to make them slightly clearer, without overly bloating the text,

• At distances smaller than 2.5 fm, the residual strong force is stronger than the coulomb force, so it is able to overcome the mutual repulsion between the protons in the nucleus. - What is the coulomb force? Not linked or explained.
  • I changed it to electrostatic force.

• The information in the first paragraph of "Nucleus" is arranged somewhat counterintuitively, with basic, easy information last.
  • I reworked the paragraph to remove some redundancy and hopefully make it easier to understand.

• The second paragraph of "Nucleus" seemed easy to grasp and I wondered if it should have been earlier.
  • I'm not sure. My preference is to have it second.

• The electron cloud is a region where each electron resides within a type of three-dimensional standing wave inside the electrostatic potential well that surrounds the much smaller nucleus. - I don't really understand this. What is a "three-dimensional standing wave"? What is an "electrostatic potential well"? I don't know about relying on wikilinks for all of this.
  • I expanded the explanation, giving seperate descriptions for potential well and standing wave. Hopefully it is clearer.

• Various analogies have been used to demonstrate the minuteness of the atom. - What follows this statement didn't seem like analogies to me - they are calculations, right? Analogies are only approximate comparisons.
  • Changed to "examples".

• Attempting to explain "spin" a little more clearly in the "Magnetic moment" section would be helpful to those of us not familiar with quantum.
  • I tried to make it a little clearer.

• The last paragraph in "Energy levels" needs to be explained more fully - it really just names effects.
  • Done.

• At temperatures close to absolute zero, atoms can form a Bose–Einstein condensate, at which point quantum mechanical effects become apparent on a macroscopic scale. - Explain - these are cool and will excite high school students.

• I feel like, overall, the article could use examples or hypotheticals to make atoms seem more concrete. It might also make the prose a bit more exciting for people who don't automatically think that atoms are the greatest thing since sliced bread. :)

• What do the editors think about including a section on "Unanswered questions about the atom"? If one audience for this page is up-and-coming scientists in high school, one way to interest them is to provide them with unsolved problems.

A clear page, which I think can be improved by a bit of expansion, a bit more explanation, and bit of pandering to the public. :) Awadewit | talk 06:21, 20 January 2008 (UTC)

Thank you for the feedback. I'll work on resolving your concerns. A problem, however, is the length constraints on wikipedia articles. It is already up to 56K in text. So I feel limited on how much this page can be expanded; much of it is summary-style, which relates to a number of your concerns..—RJH (talk) 21:19, 22 January 2008 (UTC)

Summaries are tricky. They still have to be understandable, is the thing. You might think about making a list of the ten most important things someone needs to know about atoms and working out from there. Those ten things will be very well-explained and everything else less so, on a scale of its importance, if you see what I mean. Awadewit | talk 23:51, 22 January 2008 (UTC)

Comments from Ruslik

1) In the lead I found An atom is classified according to its protons and neutrons: the number of protons determines the chemical element and the number of neutrons determines the isotope of that element, which is wrong. Atoms are classified by number of protons (Z) and the by full number of nucleons (A)—¹³C.

While it is true that the mass number is the one usually given when naming an isotope, I don't think it's wrong to say that the number of neutrons determines the isotope (it is trivially related to the mass number). Moreover, the chart of the nuclides does "classify" by number of neutrons, as it usually gives the number of protons in one axis and the number of neutrons in the other. --Itub (talk) 15:20, 23 January 2008 (UTC)

2) In the 'Nucleus' I found:

a) Nuclear fusion occurs when additional protons or neutrons collide with the nucleus. Why protons and neutrons? Nuclear fusion can occur when any two nucleuses collide.

Fixed.

b) Nuclear fission is the opposite process, causing the nucleus to emit nucleons—usually through radioactive decay. Nuclear fission is process when a nucleus splits into two unequel parts—daughter nuclears. For instance, U can split into Ba and Kr.

Fixed.

c) In atoms with high or very low ratios of protons to neutrons, the binding energy becomes negative, resulting in an unstable nucleus. I am not aware of any nucleus that has a negative binding energy. Even the most unstable nuclears still have positive binding energies.

The cited reference has a table that shows some nuclei with negative binding energy. But yes, I'm not sure what benefit that sentence has, other than a theoretical/curiosity factor. Maybe it's of interest in high energy physics?

I see you removed the sentence, so it doesn't matter much anymore. But I'm curious--where is this table? I haven't been able to find it. The only nuclei with "negative binding energy" that I can think of are things such as He-2 (because a proton really doesn't bind to another proton in the absence of neutrons!). --Itub (talk) 09:12, 6 February 2008 (UTC)

d) The last two paragraphs partially duplicate each other (binding energy and yield of the thermonuclear reactions).

Fixed.

3) In 'Electron cloud' I found a sentence: as other possible wave patterns produce interference effects that would destroy the standing wave. Please, remove it. It lacks any meaning.

The reference states that all "orbits that do not have the electrons wavelength 'fit' are not possible, because wave interference will rapidly destroy the wave amplitude and the electron wouldn't exist anymore." I'm merely rephrasing it. To me the question it raises is somewhat interesting: how does the electron "know" what orbitals are stable? It must be able to evaluate them somehow. So it makes some intuitive sense to have the non-viable states eliminate themselves.—RJH (talk) 20:39, 28 January 2008 (UTC)

The right explanation is: The electron wave function can be chosen absolutly arbitrary. However if the wave function is different from all eigenfunctions, it can be expanded in a series of eigenfunctions. Since the lifetimes of various states are different, sooner or later the electron will be in a state described by the eigenfunction with the longest lifetime. Ruslik (talk) 17:35, 29 January 2008 (UTC)

Thanks. That's going to be a bit of a challenge to explain to the non-physics reader. I'll see what I can do.—RJH (talk)

4) In Properties/Size the two sentences: The smallest atom is helium with a radius of 31 pm, while the largest known is caesium at 298 pm. Although hydrogen has a lower atomic number than helium, the calculated radius of the hydrogen atom is about 70% larger lack any citations.

5) In Properties/Radioactive decay I found

a) Alpha decay is caused when the nucleus emits two protons and two neutrons, forming a helium nucleus, or alpha particle. The result of the emission is a new element with a lower atomic number, which implies that two protons and two neutrons are emmited and somehow form an alpha-particle after that. In fact, the alpha-particle is emitted fully formed. Alpha-particles can exist inside nucleus, at least temporary. There is even a cluster model of nuclear structure, where the nucleus is represented as a sum of several alpha-particles. This model is very succeseful for some nucleuses, for instance, for ²⁰Ne=¹⁶O+α.

b)There are a number of less common forms of radioactive decay which result in emission of some of these particles by other mechanisms, or different particles. I known only two additional forms: emission of single protons/neutrons or spontanious fission. I think it is better to add them to the list above and remove this sentence.

What about positron emission, electron capture, and double beta decay? There are even papers discussing possible C-14 emission.[2] --Itub (talk) 15:20, 23 January 2008 (UTC)

Positron emission is already mentioned in 'beta-decay'. Electron capture is actually the same process. It is not materially different from the emission of a positron. Double beta-decay? It is so rare.

In fact, all these processes belong to one broad category—beta-decay. So there are only two additional forms of the radioactivity. Ruslik (talk) 07:48, 24 January 2008 (UTC)

6) The subsection Properties/Magnetic moment is not very good.

a) It states The spin of an atom is determined by the spins of its constituent components, and how the spin is distributed and arranged among the sub-atomic components, which is wrong. The spin of the atom (if you mean by spin the full moment) is sum of the spins and orbital moments of all particles .

b) It also states The spin of an atom determines its magnetic moment, and consequently the magnetic properties of each element, which also wrong. Compare magentic moments of a proton and neutron—they are very different, although spins are the same.

c) Describing ferromagnetism the subsection states that In ferromagnetic elements such as iron, the orbitals of neighboring atoms overlap and a lower energy state is achieved when the magnetic moments are aligned with each other. When the magnetic moments of ferromagnetic atoms are lined up, the material can produce a measurable macroscopic field. Actually spins of electrons are aligned, not magnetic moments. The magnetic moments are also aligned of course creating macroscopic magnetic field. The difference is subtle but important, because the alingment of spins would happen even in the absence of magnetic moments—it is caused by the coulumb interraction. In addition, orbital moments (and the respective magnetic moments) don't align.

Okay. I made some changes per your suggestions and I also asked the Physics Wikiproject if they could review the section and fix any inaccuracies.—RJH (talk) 20:36, 8 February 2008 (UTC)

7) In Properties/Energy levels there is sentence When a continuous spectrum of energy is passed through a gas or plasma, some of the energy is absorbed by atoms, causing electrons to change their energy level. It is only true in the absence of ionisation. When the energy of photons is higher the the ionisation edge, the absoption will be continuous.

I clarified that this only applies to electrons that remain bound.—RJH (talk)

8) 'Applications' section seems to be rather strange. What are the applications of the objects, which all materials and bodies in this universe are made of? This section can only be either too trivial or too complicated.

The author was trying to provide example of uses for individual atoms. When this appeared I was hesitant to just remove it, but I don't think it can be readily expanded either.—RJH (talk)

9) In the 'Origin and current state/Nucleosynthesis' there is a phrase—theoretically created, which sounds odd. Write simply 'appeared'.

Okay.—RJH (talk)

10) The 'Origin and current state/Earth' subsection is full of trivia.

I find myself having difficulty agreeing with this as an objection. Most of the information in that section is of interest, albeit not terribly challenging. Perhaps you could point out the particular points you find objectionable?—RJH (talk)

The last paragraph can be removed. It is also interesting that this subsection is called 'Earth', while the main article is 'History of the molecule'. Ruslik (talk) 18:53, 31 January 2008 (UTC)

Fixed by moving it to the molecule page. They can deal with it as needed on that page. The main article link was a vestige of an earlier organization; I removed it as there is no better substitute that i could locate.—RJH (talk)

I hope my comments will be helpful. Ruslik (talk) 15:01, 23 January 2008 (UTC)

Thank you, they were.—RJH (talk) 20:36, 8 February 2008 (UTC)

Ok, I think my comments have been addressed. Ruslik (talk) 08:42, 9 February 2008 (UTC)