Talk:Atom/Archive 3

Archive 1

Archive 2

Archive 3

Archive 4

Archive 5

Anti-Realism

Is there not a place in this article for a section on philosophical anti-realism about atoms? Judging by many of the comments in this talk page there seems to be much confusion surrounding their ontological status. Nicander (talk) 21:00, 20 January 2008 (UTC)

Atomic orbital wavefunctions illustration

The illustration of the atomic orbital wave function is lovely to look at, and I get a real sense that I am seeing something important... except I have no idea what it is. Am I looking at a photgraph of an atom? I suspect not. Are the dark areas nothing and the lighter areas something? Probably. Am I looking at a theoretical model or an image generated by some clever device which can observe the heart of a single atom? Or have I got that all wrong and maybe I should think of the illustration as some form of graph showing the theoretical increase and decrease in some quantity over the two dimensional plane? Are the images slices through something which has a three dimensional existence? I assume so, but how does the slicesomehow spin? Is that a real three dimensional spin as with a roundabout, or some notional spin which has a different meaning than the one which Mr and Mrs Average might understand?

When an electron 'leaps' from one shell to another, does it drift from one of those hazy glowing areas to another, or does it snap from the one to the other in an instant, or have I got the whole thing wrong.

Should I imagine those glowing areas, spinning while at the same time orbiting the core? Is that how spin, azimuthal quantum numbers and orbital angular momentum relate to each other?

It is tempting to say, "I am pretty intelligent yet I don't understand this stuff, so your explanation must be wrong" but I am willing to accept my share of dimness here if somone with better understanding can shed some light on this area.

I would much appreciate it!

Sign your comments, please. Too many questions to answer all at once. For atomic orbitals, you're looking at basically a 3-D graph of a math function, which outputs probability density of an electron being in a certain volume, and you're seeing this probability as brightness (color is for show). The math functions have been generated as solutions to the Schroedinger equation for hydrogen. Each function is something like a picture of where a pair of electrons is most likely to be in space, in an atom. Each of those areas (orbitals) is either one or two electrons, all smeared out. When electrons go from one to region another, they don't do so in an instant. They're moving at some good fraction of the speed of light which varies from something on the order of 1/130th to 2/3rds or so (the inner electron of a uranium atom is bound at 132 kev which is something like 30% of its rest mass, which works out to around .63 c). So that's the speed with which electrons "hop" from one of these regions to another. But once in a region, an electron is everywhere at once there, in that funny quantum way. No, these things don't spin as they orbit the core. The orbital spin is already taken care of, in their lobed shapes. Which turn into ring-like donuts at very, very high spin. For lower spin, you're just seeing some kind of odd wave-like hybrid of a donut and the fuzzy globular ball that means no spin. SBHarris 05:39, 8 November 2006 (UTC)

My understanding is that an electron 'in principle has a vanishingly small probability of being detected anywhere. It therefore "extends" through a large region of space. However, it does not do so evenly. The coloured regions are places where the sum (intergral) of the probabilioties is greater than some number - usually 90% or so. So the probability cloud extends out beyond the bubble, but 90% is inside it. And I suppose that answers the questiuon about the tiume it takes to "move" - it is not moving from place to place at all. —Preceding unsigned comment added by 164.97.245.84 (talk) 03:56, 21 January 2008 (UTC)

First paragraph: meaning of "atom"

From Wiktionary:

• Etymology of tomography: Greek tomos (slice) + graphia (describing)
• Etymology of atom: From Old (and modern) French atome, from Latin atomus ‘smallest particle’, from Greek ἄτομος, noun use of an adjective ‘indivisible’, from α- ‘without’ + τέμνειν ‘to cut’.

From Encarta:

• [16th century. < Latin atomus < Greek atomos "unable to be cut" < temnein "to cut"]

I teach quantum mechanics, I have published numerous papers on its interpretation in peer-reviewed academic journals, and IMHO one of the most important implications of quantum mechanics is that dividing a material object is no longer the same as cutting it, which was taken for granted ever since people began thinking about the divisibility of matter. I don't quite understand why my edit of the first paragraph was undone. Since no reason was given, I restored it. How do others feel about it? If I am given a good reason for rejecting my edit, so be it.

Note: I have to do further work on the cookie cutter paradigm, to which article I have included a link here. Please check it out after a day or so. --Ujm 03:32, 17 October 2006 (UTC)

History of atomic theory and discovery of atomic structure

Robert Boyle mentioned in his writings entitled Origine of Forms and Qualities in 1666 he believed there was one kind of "Catholick or Universal Matter" than existed in the form of tiny corpuscles of different sizes, shapes and motions, and these corpuscles had different properties that caused different chemical substances to have different properties. He also extended the notion these corpuscles could bind together in small clusters. I suggest to consider revising the history of the atom to include this. 71.243.188.91 02:42, 13 April 2007 (UTC)Jeff Torgalski71.243.188.91 02:42, 13 April 2007 (UTC)

Mendeleyev?

Why is Mendeleyev not mentioned in the article? Surely he did a great deal in uncovering the structure of atoms. —The preceding unsigned comment was added by 212.238.247.196 (talk) 00:11, 7 December 2006 (UTC).

Yeah, and why doesn't it mention that when Democritus created the theory, it got turned down because Aristotle proposed another theory? Yctaabpjic 08:24, 18 January 2007 (UTC)Yctaabpjic Jan.18/2007

This article contains just a very short overview of the history; for more details, you should go to atomic theory. However, that one doensn't mention Mendeleev or Aristotle (or Gassendi, Descartes, Pauli, Fermi, and many others which contributed in one way or another) either. Maybe one day I'll add some of these people if I have time... Itub 12:34, 18 January 2007 (UTC)

I agree. Even a short overview MUST include mendelev (funny how many different spellings I have seen). In my opinion, it is more relevant than heisenberg is. --RdRkX80 17:25, 2 November 2007 (UTC)

On second thought, Mendeleev is more relevant to elements than atomic theory, let alone the atom itself. --RdRkX80 17:30, 2 November 2007 (UTC)

Proton, Neutron, and Electron Quantities

I would like to see a basic explanation of the methodology used to determine the number of protons and neutrons in a particular atomic nucleus, and the same for the number of electrons that are said to be associated with it. From what are those numbers derived? Take any element in the periodic table. A particular element is said to have so many protons, and so many neutrons in the nucleus. How was that information discovered and when? A particular element is said to have so many electrons. How was that information discovered and when? 71.109.126.112 04:38, 13 January 2007 (UTC)Seeker

The closest answer to who and when for protons is Henry Moseley in 1914. He's the guy who discovered that atomic number is very nearly the same as nuclear charge, which means the number of the element in the periodic table is the number of protons in the nucleus. Rutherford had previously found charge on the nucleus was roughly half atomic weight. And also the number then of electrons in the outer atom, since they have to be equal. See the wikis on Rutherford model, Rutherford scattering and Bohr model for more. As for numbers of neutrons, that had to wait for discovery of the neutron in 1932 by Chadwick. After that, the composition of the individual nuclides was obvious from application of mass spectroscopy of their isotope masses. But a lot of people were involved in the work. SBHarris 04:55, 13 January 2007 (UTC)

Thank you for responding to my question. Could you please clarify your reference to mass spectroscopy? When I looked at the linked article I found that it appears that mass spectrosophy requires prior knowledge of atomic weight/composition. For example, "Different compounds have different atomic masses, and this fact is used in a mass spectrometer to determine what chemicals are present in a sample." It sounds like you need a set of prior facts about the content of the nucleus if you are going to make anything out of this mass spectroscopy. In this regard, it does not seem like this would be part of the answer. Please clarify. 71.109.126.112 02:36, 15 January 2007 (UTC)Seeker

The statement you refer to really only applies to molecular mass spectroscopy. In mass spectroscopy of single atoms as ions, the deflections are fully specified in terms of the well-known physics of the behavior of mass and charge moving at some velocity in a magnetic field, so that the mass/charge ratio of individual atoms can be directly calculated. If the charge on them is known (or is assumed to be one unit) then this allows direct calculation of isotope masses. For example, in 1920 it was observed (by JJ Thomson, as I recall, though he didn't initially realize what he was seeing) that there were two kinds of neon atoms, and they differed in mass by about two atomic mass units (i.e., by about the mass of two protons, as neutrons were not then known). SBHarris 03:42, 24 February 2007 (UTC)

~10⁸⁰ atoms in the universe?

Ummm...any proof of that? —The preceding unsigned comment was added by 89.252.226.19 (talk • contribs) 14:21, 14 January 2007.

Proof? Well, I was counting - but now you've distracted me so I'll have to start over...

Or, did you mean, is there a reference to support that estimate? Probably, but I don't know where. Got rid of all those zeroes - were there eighty of them? Did you really count them? Cheers, Vsmith 14:58, 14 January 2007 (UTC)

OK - I asked Google. See: http://www.madsci.org/posts/archives/oct98/905633072.As.r.html - the madsci supports the wiki number - and http://answers.google.com/answers/threadview?id=352789 - Seems there are less than a googol of them. Onward into the unknown... Vsmith 15:14, 14 January 2007 (UTC)

The scientific chain behind this is pretty solid. We know pretty accurately from Big Bang Nucleosynthesis and from measurements of the cosmic microwave background what the density of nucleons (protons and neutrons) in the universe is. This density is much less than the mass density of the universe, which is a strong pillar for dark matter. We also know from nucleosynthesis and from stellar spectroscopy that nearly all those protons and neutrons are in a mixture of ~25% Helium4 and ~75% Hydrogen (by mass) with only traces of everything else. For every sixteen nucleons, there are 12 Hydrogen atoms and one Helium atom, so the number density of atoms is 13/16 the number density of protons and neutrons.

To move from a density to number of atoms, we need to define the size of the universe and there are a couple of possible versions of that. But a good value would be the subset of the universe which we can see in principle, the event horizon. The volume of the universe within the event horizon was pretty uncertain until recently, but now with measurements of cosmology coming in from supernovas and the microwave background, is pretty certain. So today I'm sure that one could estimate the number of atoms in the universe to better than an order of magnitude of accuracy. David s graff 17:10, 30 August 2007 (UTC)

For clarity: I think David meant the number density of atoms is 13/16 the number density of (protons PLUS neutrons). Equivalently 13/2 the number density of neutrons or 13/14 the number density of protons.LeadSongDog 17:34, 25 September 2007 (UTC)

So how come when I clicked on the reference and read through it, it said 4x10^79 ie: 4 followed by 79 zeroes?? and not 10^80 which the article states? —Preceding unsigned comment added by 58.104.3.80 (talk) 01:46, 24 November 2007 (UTC)

Picture of an atom

It would be really nice to have a real image of an atom. I know it is done, I even think I saw it in O'Hanian.

Are you referring to having an accurate diagram of an atom, or an image of an atom made from a Scanning tunneling microscope (or equivalent)? Iotha 02:53, 26 January 2007 (UTC)

"If an apple was magnified to the size of the Earth, then the atoms in the apple would be approximately the size of the original apple." - If satilites can view people from outer space, then surely we will soon have the technology to see the atoms in an apple? (Seb-Gibbs) —Preceding unsigned comment added by Seb-Gibbs (talk • contribs) 21:22, 23 January 2008 (UTC)

Atoms are smaller than the wavelength of visible light, so even if you had an unbelievably powerful microscope, it will always be impossible to see without special imaging techniques (that's why we use electron microscopes). 24.131.183.162 (talk) 17:39, 10 February 2008 (UTC) darkstaruav, 10 February, 2008

You can see a picture of a concept of the atomic nuclei on Talk:Nuclear model. WFPMWFPM (talk) 16:22, 17 May 2008 (UTC).WFPMWFPM (talk) 21:24, 27 May 2008 (UTC).WFPMWFPM (talk) 21:31, 27 May 2008 (UTC)

Patents .. put in after lock out is lifted

• U.S. patent 2,516,418
• U.S. patent 4,074,443
• U.S. patent 2,601,729

172.144.93.87 21:56, 17 February 2007 (UTC)

mergto proposal Atomos

this is the Greek origin of the word atom, already explained in atom V8rik 21:16, 23 February 2007 (UTC)

well i have a question about atoms. since there is alot of space between the center and the electrons, then whats inbetween? it can be air because air is made of atoms so whats in between there? sry that i put the question here, its just i could think of any other way to put it in other then this way.

I assume you meant "it can't be air..." As for what IS in the space between the nucleus and the electrons, the answer is...nothing. Empty space. Or perhaps quantum foam, if you believe in that sort of thing. :-) 24.6.66.193 (talk) 13:34, 21 November 2007 (UTC)

Large number names

In the reference section, there is a quote: "There are 2,000,000,000,000,000,000,000 (that's 2,000 billion billion) atoms of oxygen in one drop of water—and twice as many atoms of hydrogen." The proper way to read that number would be 2 sextillion, not 2 billion billion. See Names of large numbers for reference.

Of course, in the real world, we call that number 2 × 10²¹. --Itub 09:48, 12 March 2007 (UTC)

While your at it see Long and short scales. Billion, trillion, etc. have regionally different meanings, so should be avoided where possible, or at least the scale used should be explicitly stated. LeadSongDog 17:28, 25 September 2007 (UTC)

Missing images?

There are a lot of missing images. It appears they should be there as what looks like code is present for them. A picture says a thousand words. 71.224.244.205 20:37, 16 March 2007 (UTC)Bryn.

Can an atom be charged?

Is a Na⁺-ion atom? —The preceding unsigned comment was added by 80.186.187.254 (talk) 18:30, 20 March 2007 (UTC).

I think that in most usages, charged and neutral atoms are both permitted, ie, ions are regarded as a species of atoms (charged ones). See the wiki on section on exotic atoms for even odder ones. —The preceding unsigned comment was added by Sbharris (talk • contribs) 20:04, 20 March 2007 (UTC).

Thanks for answering. Thats what I think too. But in Finland we teach in secondary school that atoms have as many protons as electrons. And I would like to check this thing and be sure. IUPACs golden book definition: http://goldbook.iupac.org/A00493.html There is nothing about the numbers of protons and electrons.

Yes. From CRC Handbook of Chemistry and Physics (58th ed.) "Definitions and Formulas": Ion.-An ion is an atom or group of atoms that is not electrically neutral but instead carries a positive or negative electric charge. LeadSongDog 17:22, 25 September 2007 (UTC)

Sorry

I would like to apologize for the whole "My name is the." edit. I know it was done several months ago, but I felt it deserved some sort of compensation. It was not done by me, rather somebody I personally know who is now a respectable member of the Wikipedia community.Supernerd 10 16:05, 21 April 2007 (UTC)

Print problem

On page 5 of this article, text fails to wrap around graphic when printing. Needs attention from editor more savvy than me. 71.232.133.137 15:54, 23 April 2007 (UTC)

Dubious claim in regards to first philosophical statement on atoms

I am removing this:

"The first philosophical statements relating to an idea similar to atoms was developed by Democritus in Greece in the fifth century BCE around 450 BCE. The idea was lost for centuries until scientific interest was rekindled during the Renaissance Period."

Any basic research, especialy on the wikipedia article on atomism, will show that the Indian schools of atomism pre-date the Greek schools. —Preceding unsigned comment added by 67.101.232.95 (talk) 02:38, 11 July 2007

Reworded and replaced. Vsmith 03:53, 11 July 2007 (UTC)

--V. 01:24, 23 July 2007 (UTC)== Dubious claim about Indian philosophy ==

I'll change back to the original "The first philosophical statements relating to an idea similar to atoms was developed by Democritus in Greece in the fifth century BCE around 450 BCE. The idea was lost for centuries until scientific interest was rekindled during the Renaissance Period." until someone can show some actual research about these legendary Indian philosophers. Nationalist internet articles doesn't prove anything and they are definitely not good enough sources for an article in an encyclopedia. —Preceding unsigned comment added by Joe hill (talk • contribs) 22:13, 13 July 2007

What dubious claim? Did you read the Wiki article on atomism? And who said anything about nationalism? The Greeks *themselves* acknowledged the Indian influence, as evidenced by "The Shape of Ancient Thought" by Thomas McEvilley, who is *neither Hindu nor Indian*. It is an undeniable fact that the Greeks, regardless of the Eurocentric version of history that many subscribe to, were heavily influenced by the Indians, Mesopotamians, and Egyptians and much of their metaphysics is simply a regurgitation of what was already known or philosophized upon. Buy the book(s) and learn.

Here is the link

Here is the link from "The Shape of Ancient Thought". :::http://books.google.com/books?id=K47gmG7tJ1UC&pg=PA318&lpg=PA318&dq=the+shape+of+ancient+thought+atoms+india&source=web&ots=VlEfIf3ZW9&sig=Hy0b3ZKAvbhfKb7e_hijryfccvg

rams81 18:00, 16 July 2007 (UTC)

It should at this point be noted that the concepts found in Indian and Greek philosophy in no way resemble the concept of an atom as we know it today. They posed purely on philosophical grounds that there are elementary particles which in different combinations form all the world. Other than the name, the scientific concept has nothing to do with the philosophy of atomism. I think in the history section of this article on the scientific atom the indian and greek philosophy is overstressed. --V. 22:40, 20 July 2007 (UTC)

I made the section on indian atomism a little shorter. This information is also available on both atomism and atomic theory. no need to repeat here. also it is not relevant to the the modern concept of the atom, which (according to the introduction) this article is about. --V. 01:24, 23 July 2007 (UTC)

Measurements

Can remove the Angstrom and replace it with modern measurements? I would rather you show the measurements in nanometers or smaller as this is the standard measurements used today and is the SI unit.

I disagree. Angstroms are still used today to discuss sizes of things like atoms. They are fundamentally an SI unit as well, or at least have a simple definition in terms of SI units. David s graff 16:55, 30 August 2007 (UTC)

Agree. From Angstrom: Today, the use of the Ångstrom as a unit is less popular than it used to be and the nanometre (nm) is often used instead (with the Ångstrom being officially discouraged by both the International Committee for Weights and Measures and the American National Standard for Metric Practice).LeadSongDog 17:17, 25 September 2007 (UTC)

Replaced Big Bang

I felt that the previous section on the Big Bang, while largely correct, was only tangentially related to this article. I greatly simplified it and folded into (I hope) a much more relevent section on the origin of atoms. The details of big bang nucleosynthesis are important of course, but they belong in the article, and a link and summary should suffice here. And I didn't feel that they were more important than the origin of other atoms, especially since very few of the atoms generated during big bang nucleosynthesis are present today on earth (basically just the deuterium). The ideas in the deleted section would worth spelling out in more detail in a seperate article on the origin of atoms, but I felt that the pre-existing article on nucleosynthesis serves that function well. David s graff 16:53, 30 August 2007 (UTC)

But it's not just the D. The ratios of H and He-4 in the solar system are BBN ratios, so most of these are from there-- the ordinary H in your water is BBN-primordial too!. Most of the He-4 on Earth (99%) is from radioactive decay, but not that in the Sun or Jupiter, so don't be an Earth-chauvanist. Most of our Li-7 is BBN generated also, which means most of the Li, which is mostly Li-7. We can't even rule out some Be production in BBN. All we know "for certain" is no C or anything bigger. SBHarris 23:57, 11 November 2007 (UTC)

Urgent need of adding information about SYNTHETIC ATOMS

Today I've been reading about synthetic atoms, but unfortunately the information available in Internet is very weak and escase. Good information is, as always, in sites type "pay per view", as Elsevier, Springer, etc.

Someone could add reliable information about Synthetic Atoms? Don't know if the information should be added to this article, or even creating a new one specifically on the subject.

Define fission

Atom#Nucleus says "Nuclear fission is the opposite process, causing the nucleus to emit some amount of nucleons—usually through radioactive decay." I think this is saying that radioactive decay is defined to be a kind of nuclear fission. That's not what I thought fission meant. Compare Nuclear fission#Physical overview: "Nuclear fission differs from other forms of radioactive decay..." which says the opposite, that nuclear fission, even in an atom bomb, is defined as a form of radioactive decay. Here's a dictionary definition of nuclear fission: "the splitting of the nucleus of an atom into nuclei of lighter atoms, accompanied by the release of energy." We should keep our semantics consistent one way or the other. Art LaPella (talk) 06:44, 17 November 2007 (UTC)

Warth

I moved this comment from the top of the page to the bottom, where it belongs, and explained the move on Supineny's talk page. Art LaPella (talk) 03:10, 22 November 2007 (UTC)

i don't seem entitled to edit this article, but i'd point out that the word "Earth" seems to be misspelled towards the end, as "Warth". Unless that's something else... Supineny (talk) 22:05, 21 November 2007 (UTC)

I fixed "Warth". You should be able to edit the page yourself. What happens when you go to Atom and click the "edit this page" near the top of the screen (as you must have done to edit this page)? Art LaPella (talk) 03:10, 22 November 2007 (UTC)

Volume of the atom

Isn't the distance between the nucleus and the electrons of an atom relatively huge? And isn't the majority of the volume of an atom nothingness? I tried to find some section in the article concerning this, but could not, and I think it might be a good idea to add such a section. However, I don't know if I'm missing something either in my understanding of the theory or in my assessment of what is already on Wikipedia. -albrozdude 18:41, 1 December 2007 (UTC)

The relative sizes are now mentioned in the first paragraph of the nucleus section. I'm not whether you can categorize the remaining space as nothingness as it is still occupied (in the probability sense) by the electron cloud. It is just much "less dense" than the nucleus.—RJH (talk) 21:57, 14 December 2007 (UTC)

Cannot be Split?

Quoting the article:

"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 still characterizing a chemical element."

This cannot be right. you can split an atom. And when you do, you create a massive nuclear explosion. This is how they make WMDs (weapons of mass destruction, aka - nuclear bombs). This is freaky. Someone should edit the article.

KT529 16:10, 4 December 2007 (UTC)

That quote is saying the origin of the word "Atom". They thought you could not get smaller than this. It is now known we can split them, however that quote is what the word means. Dodo48 (talk) 03:52, 9 December 2007 (UTC)

Yes, they merely got the name wrong (used it too early). Nowadays we'd probably call quarks and leptons after the Greek "atomos," if it hadn't already been used. But who knows-- perhaps one day they'll be found to be composite also. SBHarris 22:41, 14 December 2007 (UTC)

To-do

Personal to-do list:

• Conductivity. -> skipped.
• Wave behavior of atoms.
• Spectral lines, spectroscopy and stellar opacity.
• Particle (atom) trap.
• Antimatter atoms.
• Island of stability.
• Plenty of references.

—RJH (talk) 22:15, 19 December 2007 (UTC)

Atoms versus elements

There seems to be quite a bit of overlap here between Atom and Chemical element and I think a clear distinction needs to be drawn. The element page is focused on the differences between elements, their arrangement and abundance, etc, whereas atom should be on the physics and chemistry of the atom as a unique, inclusive entity. I added some things on spectroscopy and identification here but I'm not 100% sure they're appropriate. Thoughts? Furmanj (talk) 13:40, 23 December 2007 (UTC)

I'm not sure how you can cover atoms in a comprehensive manner (per the featured article criteria) and not also discuss elements and isotopes. To me a good part of this page is written summary style, so I think some overlap is acceptible as long as the details are left to the sub-pages.

For example, a discussion of valence is appropriate in the context of the electron shells. Possibly the information about chemical bonds is a little out of scope and could be culled. (I added that in knowing that it may get reduced down later during final edits; better too much than too little.) But in its place, for example, I would be interested in information about why an atom interacts so as to have its outer shell filled.—RJH (talk) 20:21, 23 December 2007 (UTC)

Careful! There's thorough and good article on chemical bond for that. And you don't want to get sucked into chemistry, isotopes, and atomic physics, except as you can do it with a REALLY short summary sentence and some main article directs. Most things are made of atoms, so the temptation for subject creep is especially bad here. SBHarris 22:12, 25 December 2007 (UTC)

Okay I've cut back most of the discussion of chemical reactions in the "Valence" section.—RJH (talk) 17:34, 1 January 2008 (UTC)

Question about image of atoms

In the article there is an image that is said to be a picture showing individual atoms, is this true? Does this picture actually show the atoms that make up that sheet of gold?

Sorry if this isnt the propper way of asking this, but I'm just dumbfounded by this, as far as my limited knowledge went, they hadnt been seen nor pictured in any form yet. 200.109.43.50 (talk) 01:09, 4 January 2008 (UTC)

Yes, images which represent atoms have been generated for several years. I think the probe is actually detecting the electric field of the atom's electrons at very close range, but I'd have to go read up on the technique to confirm that. The image is resolving things which are the size of atoms, whatever the technology is actually doing; it's equally amazing whether electrons, photons, or X-rays were being used to create the image. -- SEWilco (talk) 02:04, 4 January 2008 (UTC)

You're actually looking at a map of electron density (the probability that an electron exists in that location), not a 'snapshot' image of a physical surface (which, after all, doesn't really exist in the way a surface of a macroscopic ball exists) Furmanj (talk) 11:48, 4 January 2008 (UTC)

Nobody has an "Image" of an atom. What is available are images of concepts of atoms from which you are supposed to make your preference. We also have a set of "combined facts and/or opinions" which are the suggested criteria for making such a selection. While doing so, I suggest that you learn as much as you can about the physical events occurring in the volumes of space where atoms are being created. The most notable one I can find is the Hubble images of the center of the Whirlpool Galaxy (M51). If you want an image of a concept, I recommend that you look at Talk:Nuclear model WFPMWFPM (talk) 23:48, 14 May 2008 (UTC)WFPMWFPM (talk) 14:06, 15 May 2008 (UTC)WFPMWFPM (talk) 21:42, 27 May 2008 (UTC)

Examples need references

I searched around but I was unable to uncover the original references for these examples. Hence I am moving them here until an original source can be produced.

• An HIV virion is the width of 800 carbon atoms and contains about 100 million atoms total.
• An E. coli bacterium contains perhaps 100 billion atoms, and a typical human cell roughly 100 trillion atoms.
• A speck of dust might contain 3 trillion atoms.

The HIV virion has a mean width of 125 nm and is roughly spherical, giving an approximate width of 1,250 carbon atoms and a volume of a billion carbon atoms. So both the width and the number of atoms appears too small. The other two examples may or may not be correct. Some additional cited examples may be helpful in their place. Sorry.—RJH (talk) 22:11, 7 January 2008 (UTC)

I don't think the number is excessively small, but a reference is certainly desirable. You are assuming that HIV is made of perfectly packed cubes 0.1 nm on a side. Yet the C-C bond is 0.154 nm (probably such a value was used for the 800-atom estimate, although a point can be made that carbon chains are not straight and therefore a simple division by 0.154 nm is wrong), and the packing is not perfect. For example, if we assumed that the virion were made out of diamond (I know, a bit of a stretch ;-), with the diamond unit cell being 0.357 nm and containing 8 atoms, a sphere 125 nm in diameter would contain about 180 million atoms.

I don't have a reference for HIV, but here is one for the (much smaller) satellite tobacco mosaic virus, which is known in atomic detail and has about 166,000 atoms. See [1] and [2]. Note that the "1 million" figure quoted in the abstract and the website includes solvating water molecules, which account for about 900,000 atoms; you have to look at the text of the article for details. --Itub (talk) 12:09, 9 January 2008 (UTC)

Thanks. I had seen a much older estimate of the tobacco mosaic virus but it appeared to be well off the modern value for the dimension. A modern reference is helpful.—RJH (talk) 20:15, 9 January 2008 (UTC)

External Links

I think we could use a few more external links. I've found a few I thought would be good but maybe someone would like to review them first before putting them up?

• [3]
• [4]
• [5]

Furmanj (talk) 20:51, 9 January 2008 (UTC)

My personal preference would be to only include on-topic external links that provide interesting reading beyond what is covered in the article. Otherwise the FA reviewers may ask for the number of links to be cut down (or worked into the list of references). The 1st, 3rd and last links seem too trivial. I could not access the 5th and 6th links, so they are unacceptible. That would leave possibly the 2nd and 4th.—RJH (talk) 21:39, 9 January 2008 (UTC)

I've cut 5. Link 6 was down yesterday but appears to be working again and I think is fairly useful. Give it a look. Furmanj (talk) 06:48, 10 January 2008 (UTC)

Okay, I noticed that the last (ParticleAdventure) link in your revised (unfortunately re-bulleted) list is already in the list of references. (Reference note #24.) In fact the references section now contains a significant number of external links, many of which make for interesting reading.—RJH (talk) 15:41, 10 January 2008 (UTC)

Revision of diagram

I revised the labels on the images to include both arrows and to put all the numbers in nanometers. Thoughts?

Furmanj (talk) 19:15, 12 January 2008 (UTC)

Helium atom ground state

The concern I would have is that the 10^-7 is not going to be legible once the image is reduced in size.—RJH (talk) 18:47, 13 January 2008 (UTC)

Czech version

The picture is not very corect, the decay of electron probability should be approximately e^-x but on the picture is linear and has no derivative on the border which is not alowed for wavefunction see czech version http://cs.wikipedia.org/wiki/Soubor:Helium_atom_QM.png which is much better

The only issue with the Czech version is that the resulting electron cloud distribution is almost too faint to see across most of the image. But perhaps that is not a significant issue, and it looks pretty good overall. Would anybody object to using the Czech version of the image instead of the current image?—RJH (talk) 14:47, 11 April 2008 (UTC)

How to reference

The following paragraph contains such sweeping generalizations that I'm having difficulty trying to reference it. Does anybody have some suggestions? If not I'm contemplating just replacing it.

Most of the atoms at the surface of the Earth are bound into various molecules. For gases and certain molecular liquids and solids (such as water and sugar), molecules are the smallest division of matter which retains chemical properties. However, there are solids and liquids which are made of atoms, but do not contain discrete molecules such as salts, rocks, and liquid and solid metals. Thus, most of the mass of the Earth—much of the crust, and all of the mantle and core—is not made of identifiable molecules. Rather the atomic matter forms networked arrangements that lack the particular type of small-scale interrupted order that is associated with molecular matter. That is, they form small, strongly bound collections of atoms held to other collections of atoms by much weaker forces.

Thanks.—RJH (talk) 21:22, 15 January 2008 (UTC)

Sigh. It may not be terribly clear, but it's trying to say something important, which is that that hunk of basalt you hold in your hand is made of atoms, but not molecules. Most inorganic solid substances you see in nature here on Earth, from rocks to metals, are not made of molecules. And that includes almost all the substance of the Earth you can't see. SBHarris 22:05, 21 January 2008 (UTC)

I understand. Unfortunately I couldn't find suitable references that would validate the broadly quantitative statements: "Most of the atoms..." and "...most of the mass..." If we knew where those originated it might be helpful.—RJH (talk) 22:28, 21 January 2008 (UTC)

Well, Structure of the Earth gives lists of the substances thought to make up the various layers of the Earth, and references. None of them are molecular solids. Are we not agreed that the Earth is made of atoms and that's where its mass is (are you suggesting a black hole or a dark matter core or something??) I don't see the problem. If you want to mine 30 reference out of that article and string them behind the statement, you can, but it would much easier just to reference the other article as a (see also). SBHarris 22:44, 21 January 2008 (UTC)

I think you misunderstand my meaning, or else you're just being silly(?). What I need is a reference for the statement that: "... most of the mass of the Earth ... is not made of identifiable molecules". I don't have access to most of the references on the structure of the Earth article so I can't verify that they confirm the statement. I also don't believe I can use another wikipedia article as a reference. Thanks.—RJH (talk) 22:53, 21 January 2008 (UTC)

Who says you personally need to verify every reference before you'll accept them? The fact that you personally don't have access to those references does not mean they are not valid references. They are valid if you in theory CAN check them-- the fact that YOU are unwilling or unable to do so, has nothing to do with their verifiability or validity. What does it matter if the references are HERE or THERE? If you doubt their validity, why do you not go to the article in question and begin to delete there, citing your own skepticism, on the basis that you cannot personally get to a library to check them? I'm not being silly-- I'm making a point. I'm saying you're being skeptical and intransigent when you have no good reason to be, at all. This is not a discussion about fringe science ideas we're having here. What the Earth is made of, is not heavily debated at the general level. It's well-accepted that it's composed of various silicates with a metal core [6]. SBHarris 23:21, 21 January 2008 (UTC)

First you suggest I am saying the mass of the Earth is delivered by a black hole and then you appear to be making wild accusations that I am clinging to fringe science. Interesting. I'm just being deliberate and thorough here; I'm not challenging the findings of science.

The references are citing material that is in another article. If I can not read them, I can not see if they satisfy the particular needs of this article. I can not honestly attach a reference to an article if I haven't examined that reference to see if it confirms the statement.

After reading through the Structure of the Earth article, I see nowhere that it says the interior of the Earth is not composed of identifiable molecules. In fact it doesn't mention molecules at all. It does mention that the core is an alloy, so perhaps that is sufficient... if it can be demonstrated that the core forms "most" of the mass of the Earth. It also mentions a mantle made of silicates, but the Silicate article only mentions that it consists of a compound. The chemical compound article does appears to imply that compounds are molecules. So a curious reader might decide that a part of the mantle may be made of indentifiable molecules. How much of it consists of molecules and how much is non-molecular? How would I know? I need a reference.

The pubmedcentral reference you have above appears to be primarily about structure. Unless I missed it, I don't see a lot about the chemical composition and how it is organized.—RJH (talk) 16:21, 22 January 2008 (UTC)

That does seem unreadable and I'm not sure it contributes much. I do see what that contributor was trying to get at though, basically the distinction between a molecular solid, covalently bonded solid and an ionic solid. I'm not sure where the earth's crust figures into this, that could probably be scrapped entirely. I think what might serve us better would be a short discussion on the phases of matter with respect to the coordination and arrangement of atoms therein. Taking into it links to Phase (matter), Gas, liquid, solid, liquid crystal, amorphous solid, Correlation function, Molecular solid, etc. Furmanj (talk) 23:07, 15 January 2008 (UTC)

I managed to cobble together a replacement paragraph that allows suitable references. But yes it would make sense to have a paragraph on the different states of atomic matter. Thanks.—RJH (talk) 16:13, 16 January 2008 (UTC)

I agree with SBHarris that most of the Earth is not made of molecules. I think this is the sort of "obvious fact" that is not often mentioned in textbooks because perhaps it is not that important neither to chemistry nor to Earth science. The structure of the Earth is important, but I don't think anyone cares whether we choose to say that "most" of the components are molecular or not (especially given the existence of gray areas such as polymers). More importantly, why is this relevant to an article about atoms? Just say something like "atoms can form molecules, but atoms can also form non-molecular substances" or something to that effect. No need to get into details about the Earth's structure. --Itub (talk) 17:38, 22 January 2008 (UTC)

References & PR

Okay I think I've got this article adequately referenced now. If you would be willing, I'd appreciate any additional observations you could add to the peer review (linked at top). Thank you!—RJH (talk) 16:47, 16 January 2008 (UTC)

The PR is closed in preparation for an FAC. Thank you for your helpful comments.—RJH (talk) 18:14, 12 February 2008 (UTC)

Shape

perhaps, in the section on orbitals, the article might mention that the geometric shape of the orbitals results in molecules and crystals having the shapes they do. For instamce: it's the p orbitals of sodium and chlorine that cause common salt to have the precise rectangluar crystals that it does. —Preceding unsigned comment added by 164.97.245.84 (talk) 03:50, 21 January 2008 (UTC)

I added a brief sentence about the possible shapes of orbitals in the "Electron cloud" section. But the problem is that further details would be veering into a more extensive coverage on the topic of chemistry, which is covered in other articles.—RJH (talk) 21:07, 21 January 2008 (UTC)

It's more complicated than that, especially given that the bonding in NaCl is predominantly ionic. --Itub (talk) 21:35, 21 January 2008 (UTC)

Passed GA Review

I've done a GA review of this article and am very impressed. I did a number of minor revisions as I reviewed, and have made comments on specific sections below. As I see it, the three biggest challenges for this article are:

1. Subject bloat: as was mentioned above, umbrella articles such as this must find a fine balance between being comprehensive and leaving unnecessary details for the sub-articles. The article has found that balance, for the most part, but it may well drift in future edits.

   I've never liked that arbitrary rule about article length, but yes this article could easily become much larger. Hopefully it can be monitored and the more tactical additions could be moved to the sub-articles.—RJH (talk) 18:03, 12 February 2008 (UTC)

2. Jargon and lay accessibility: as with all scientific and technical articles, jargon must be avoided if possible or clearly explained if crucial to the points being made. Unlike many other article I've read, I can tell that the editors here have made a deliberate effort to address this challenge. Still, I found a number of passages that would be very difficult to understand for someone unfamiliar with the subject—I fixed the ones I noticed, but there are probably more I missed.

   Thank you for the fixes.—RJH (talk) 18:03, 12 February 2008 (UTC)

3. Structure: I hesitate to include this as I've only a vague sense of my thoughts on the subject. It's just, in reading through the article I had a constant feeling that there's a better way of organising the article's information. I realise this isn't too helpful without a suggestion on how to achieve a better organisation, of course...

   I'm not sure what to say to this. The current organization has a certain logic to it, in my mind.—RJH (talk)

Anyway, because overall this is a very well produced article, I've no reservations about giving it GA status, and suggest it be nominated for FA status as soon as the few comments I've made below have been considered. If it is taken to FA, drop a note on my talk page as I'd be interested in helping it get through that nomination.

Thank you.—RJH (talk)

Lead

The Lead could be tighter, i.e. each paragraph presents multiple ideas. Focus is difficult to achieve in a lead which has to support such a broad subject, but is still something to strive for.

I'm not sure how to summarize the entire article in just a few paragraphs (as required) without some subject transitions.—RJH (talk)

History

Jargon in forth para. "simple proportions" is referred to as if the reader will understand the reference. It would be better to reword the sentence to "spell out" what simple proportions means (as has been done with the other clause, "...why certain gases dissolved better in water than others). If this gets too wordy, I suggest omitting the clause.

I tried to clarify this.—RJH (talk)

Bohr model image: orbital rings are very hard to see (on my humble monitor).

Components

Nucleus

The pauli exclusion principle paragraph confused me. For starters:

1. The definition of "fermions" is unclear. Are protons the only fermions in the nucleus? If so, why can't we just say "protons"? Or, if neutrons are also fermions, why can't we just use "nucleons" which is already defined. I know fermion is more precise, but is the distinction necessary here?

   We can't say nucleons because the rule applies to identical fermions. I.e. none of the protons can be in the same state and none of the neutrons can be in the same state, but a proton and a neutron can occupy the same state since they are different fermions.—RJH (talk) 17:46, 12 February 2008 (UTC)

2. Fermion says that only charged particles are fermions, but this para says that the pauli exclusion principle applies to neutrons as well.

   The article says that half-spin particles are fermions; it says nothing about their electrical charge.—RJH (talk) 17:46, 12 February 2008 (UTC)

3. The para says "To minimize the energy of the nucleus, the lowest allowed energy levels are preferentially occupied by the nucleons", but if nucleons means neutrons and protons, what else is left in the nucleus?

   I tried to modify the paragraph to make what is going on clearer. Sorry for the confusion.—RJH (talk) —Preceding comment was added at 17:54, 12 February 2008 (UTC)

Properties

Energy Levels

The final two paragraphs in this section seemed unnecessary, so I've moved them here for review.

If a bound electron is in an excited state, an interacting photon with the proper energy can cause stimulated emission of a photon with a matching energy level. For this to occur, the electron must drop to a lower energy state that has an energy difference matching the energy of the interacting photon. The emitted photon and the interacting photon will then move off in parallel and with matching phases. That is, the wave patterns of the two photons will be synchronized. This physical property is used to make lasers, which can emit a coherent beam of light energy in a narrow frequency band.

When an atom is in an external magnetic field, spectral lines become split into three or more components; a phenomenon called the Zeeman effect. This is caused by the interaction of the magnetic field with the magnetic moment of the atom and its electrons. Some atoms can have multiple electron configurations with the same energy level, which thus appear as a single spectral line. The interaction of the magnetic field with the atom shifts these electron configurations to slightly different energy levels, resulting in multiple spectral lines. The presence of an external electric field can cause a comparable splitting and shifting of spectral lines by modifying the electron energy levels, a phenomenon called the Stark effect.

--jwanders^Talk19:22, 10 February 2008 (UTC)

These are properties of individual atoms. They are in the article for comprehensiveness; one of the requirements of the FA process. I'm going to put them back in for the FAC process. If these become an issue, they can be removed at that point. Thanks.—RJH (talk) 17:33, 12 February 2008 (UTC)

I agree those paragraphs had important information. One more comment: Fermion does not say that only charged particles are fermions. Perhaps the confusion is that it only gave the proton and the electron as examples in the first sentence, but "such as" does not imply an exhaustive list. In short, neutrons are fermions too. --Itub (talk) 17:49, 12 February 2008 (UTC)

detail

0.25 atoms/m3 or 0.25 atom/m3 ?(note the s) Randomblue (talk) 19:15, 14 February 2008 (UTC)

Yes I wasn't sure about that one. Would it be 1.99 atom/m³? It sounds awkward when spoken out loud. This page suggests that "most fractions are followed by a plural noun; e.g. 'half of the books', except uncountable nouns".—RJH (talk) 16:29, 15 February 2008 (UTC)

(ec) I always use the plural for numbers other than exactly 1 (whether smaller than 1, greater, negative, or zero). I'm not sure what the style guides would say. --Itub (talk) 16:33, 15 February 2008 (UTC)

disambiguation

the link position needs disambig Randomblue (talk) 19:23, 14 February 2008 (UTC)

Number of atoms in the Universe

I'm having a little difficulty trying to solidify this value, so I moved it here for the moment. The estimates fluctuate depending on the author and I can't find a really solid scientific paper on the topic. Here are some examples:

Number of atoms in the observable universe

Value	Reference
1079	"The Universe". National Solar Observatory. May 21, 2001. Retrieved 2008-02-15. {{cite web}}: Check date values in: |date= (help)
1080	Champion, Matthew (September 11, 1998). "How many atoms make up the universe?". MadSci Network. Retrieved 2007-01-02. {{cite web}}: Check date values in: |date= (help)
1081	deGrasse Tyson, Neil (1994). Universe Down to Earth. Columbia University Press. pp. p. 10. ISBN 023107560X. {{cite book}}: |pages= has extra text (help)

Any suggestions? Thanks.—RJH (talk) 17:29, 15 February 2008 (UTC)

Expansion of the universe? Seriously, it's a problem. First, we should qualify that we're talking only about the visible universe, because the part over the horizon is probably a lot larger, and Travelocity rates to get there are steep. But once you get the mass of the visible part down (which should be derivable from the expansion rate), you subtract dark matter (since not made of atoms), and them divide the rest by the average molecular weight of post big bang "crap", which at one He per 12 H is about 2e27 atoms per kg or so, right? SBHarris 18:07, 15 February 2008 (UTC)

I understand how it is derived and what is meant by the visible universe. What is needed is a bullet-proof reference.—RJH (talk) 19:12, 15 February 2008 (UTC)

The size and density of the observable universe were only really pinned down in this century, with the current best data from WMAP. So all these references are out of date. I could derive the number from the data given in the WMAP papers, but it would be WP:original research ;) 140.105.79.118 (talk) 15:54, 15 May 2008 (UTC)

inconsistent terminology

Sometimes Hydrogen-1 is referred to as Hydrogen-1 and sometimes as protium. Randomblue (talk) 18:42, 15 February 2008 (UTC)

Yes, they are synonyms. I think hydrogen-1 is more widely used, so it should be favored.—RJH (talk) 19:00, 15 February 2008 (UTC)

completely stable

What do you mean by completely stable in "The heaviest completely stable atom is that of lead-208"? Don't all atoms have a limited lifetime (although some are indeed quite long)? Randomblue (talk) 18:46, 15 February 2008 (UTC)

A stable element has at least one stable isotope. I added a wikilink.—RJH (talk) 19:05, 15 February 2008 (UTC)

Although in some theories protons decay, this has never been proven. Until it is, so far as we can tell, stable isotopes are stable forever.SBHarris 03:22, 12 May 2008 (UTC)

Magnified apple

The image quoted from Feynman is vivid & arresting (If an apple was magnified to the size of the Earth, then the atoms in the apple would be approximately the size of the original apple). Another one in a similar vein that I once came across is that there are as many water molecules in a teaspoon of water as there are teaspoons of water in the Atlantic (?) Ocean. It sounds very roughly the same order of magnitude, but I can't find the original reference. --NigelG (or Ndsg) | Talk 19:08, 15 February 2008 (UTC)

It's from:

Feynman, Richard Phillips (1995). Six Easy Pieces: Essentials of Physics Explained by Its Most Brilliant Teacher. Basic Books. ISBN 0201408252.

You can find it by searching google books.—RJH (talk) 20:48, 26 February 2008 (UTC)

Today's FA

I know it's many months away, but I thought I'd suggested this article for front page treatment on December 10. That is the date the Nobel Prize festivities are held. Please comment. Thanks.—RJH (talk) 20:52, 28 February 2008 (UTC)

Never mind, it got yanked because of a 30 day limit. I'll try again in November.—RJH (talk) 21:04, 28 February 2008 (UTC)

Sounds like a good plan. As the Nobel Prize isn't a great match to Atom, do we want to find a different, sooner date? Or even make a proposal without a associated date? --jwanders^Talk 21:57, 28 February 2008 (UTC)

I don't think there's a big hurry, so December 10 seems like a good match to me. We're already past the World Year of Physics, the 90th anniversary of Niels Bohr's atomic theory and the 60th anniversary of the atomic bombings of Hiroshima and Nagasaki.—RJH (talk) 22:37, 28 February 2008 (UTC)

edit to intro

I removed the statement that the wave-particle duality was used to model the atom. Though it takes no stretch of the imagination that the two are related, the statement is vague. The sentence that remains is clear and sufficient. Also I removed the reference Harrison (2003). Without a title or a publisher this could be any of a hundred articles os books. --V. (talk) 05:03, 13 May 2008 (UTC)

The Harrison reference refers to the book cited at the bottom of the article, in the "Book references" section: Harrison, Edward Robert (2003). Masks of the Universe: Changing Ideas on the Nature of the Cosmos. Cambridge University Press. ISBN 0521773512. --Itub (talk) 08:53, 13 May 2008 (UTC)

is there a specific reason that the books are separate? --V. (talk) 18:34, 13 May 2008 (UTC)

I didn't do it, but my guess is that this method is used because it allows one to have several references to different pages of the same book without excessive duplication and without using "ibid" and such. For example, ref 1 might say "Harrison (2003), p 42" and ref. 2 might say "Harrison (2003), p 89". But I don't see any book citation in this article with page number, so the separation is not really justified IMO. --Itub (talk) 18:51, 13 May 2008 (UTC)

The separation of the books into a list was requested as part of the FA candidate edits. A reviewer wanted a list that they could easily read through. (See Nigel, Wikipedia:Featured article candidates/Atom.) The reference is to the book list on this page and is unambiguous, so I restored it. If the issue is with the lack of page numbers, I can work on adding them in where appropriate.—RJH (talk) 22:26, 13 May 2008 (UTC)

Encyclopaedia Britannica

The 9th edition of the EB has two very informative articles about the Atom and the theory of the force of universal gravitational attraction by Prof. G Clerk Maxwell (Atom & Attraction) that explain the development of the classical concepts related to this subject matter. They are very much worthy of review and consideration. WFPMWFPM (talk) 23:18, 14 May 2008 (UTC)

(O/T NOTE: I fixed the format of your additions by placing it at the end, removing the blank from the start of the lines and moving the comments to a separate line from the section title. Please take a look at Help:Contents/Editing Wikipedia for more information on how to edit wikipedia. Thank you.—RJH (talk) 15:04, 15 May 2008 (UTC))

Proposed Czech image

An anonymous poster made the suggestion that we use the image at right as it uses a radial decay proportional to e^-r for the electron cloud. Is there interest in using this image in place of the current helium atom diagram? I'm not sure whether the listed units are best for this purpose.—RJH (talk) 17:15, 16 May 2008 (UTC)

I am not sure that He follows this law. Ruslik (talk) 08:23, 17 May 2008 (UTC)

Kindly clarify.—RJH (talk) 16:50, 18 May 2008 (UTC)

Electron density in He does not folllow e^-r law. Ruslik (talk) 11:12, 20 May 2008 (UTC)

Thank you.—RJH (talk) 15:06, 21 May 2008 (UTC)

Unsourced additions

The following additions, while probably correct, are also unsourced. To avoid a FAR, I would like to make sure that this page continues to satisfy the FA criteria.

Of the chemical elements, 80 have one or more stable isotopes (elements 43, 61, and all elements numbered 83 or higher have no stable isotopes). As a rule, there is, for each atomic number (each element) only a handful of stable isotopes, the average being 3.4 stable isotopes per element which has any stable isotopes. Sixteen elements have only a single stable isotope, while the largest number of stable isotopes observed for any element is ten (for the element tin).

Stability of isotopes is affected by the ratio of protons to neutrons, and also by presence of certain "magic numbers" of neutrons or protons which represent closed and filled quantum shells. Of the 269 known stable nuclides, only four have both an odd number of protons and odd number of neutrons are known: ²H, ⁶Li, ¹⁰B, ¹⁴N. Also, a very very long-lived radioactive odd-odd nuclides (⁴⁰K, ⁵⁰V, ¹³⁸La, ^180mTa) occur naturally. Most odd-odd nuclei are highly unstable with respect to beta decay, because the decay products are even-even, and are therefore more strongly bound, due to nuclear pairing effects.

It is often far easier to remove unsourced entries than it is to try and source somebody else's input, so I am hoping that citations are readily available for this material. Otherwise I think this should be pruned back. Thoughts?—RJH (talk) 15:30, 23 May 2008 (UTC)

The first paragraph can be sourced to the chart of the nuclides as it contains just trivial counting. The second one is more analytic but I'm sure can be based on any nuclear chemistry/physics book. --Itub (talk) 16:06, 23 May 2008 (UTC)

Perhaps then the CRC Handbook of Chemistry & Physics will cover both? It looks like the Table of Isotopes includes suitable information, so I'll just use that unless somebody squawks. Thanks. The only problem remaining is the use of "very very long-lived", which conflicts with Wikipedia:MoS#Unnecessary_vagueness. (Very very long-lived is 100 years to me...)—RJH (talk)

We could say "with a half-life of billions of years", or something like that. I know that's the case for K-40; I'd have to check the others. --Itub (talk) 18:02, 23 May 2008 (UTC)

Yes they're all over a billion. I think it's fixed now. Thank you.—RJH (talk) 18:04, 23 May 2008 (UTC)