Talk:Atomic nucleus

From Wikipedia, the free encyclopedia
Jump to: navigation, search
WikiProject Physics (Rated B-class, Top-importance)
WikiProject icon This article is within the scope of WikiProject Physics, a collaborative effort to improve the coverage of Physics on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
B-Class article B  This article has been rated as B-Class on the project's quality scale.
 Top  This article has been rated as Top-importance on the project's importance scale.

Atomic Decay[edit]

If a nucleus has too few or too many neutrons it may be unstable, and will decay after some period of time. For example, nitrogen-16 atoms (7 protons, 9 neutrons) alpha decay to oxygen (8 protons, 8 neutrons) within a few minutes of being created. In this decay a neutron in the nitrogen nucleus is turned into a proton and an electron by the weak nuclear force. The element of the atom changes because while it previously had seven protons (which makes it nitrogen) it now has eight (which makes it oxygen). Many elements have multiple isotopes which are stable for weeks, years, or even billions of years. It also has a positive center.

Alpha decay and cadmium-48 atom? That is too ridiculous. Someone please fix it.

The atomic nucleus[edit]

==The atomic nucleus is the result of a process of nucleon (atomic mass particle) accumulation. At long distances it is powered by the presumed forces of the gravitational accumulation phenomenon. It is an Energy conversion process, where the potential gravitational energy of a quantity of matter is converted into kinetic energy of motion on the part of the individual parts of the quantity in accordance with Newton's physical laws. However it was noted that, on occasion, these motions were added to or opposed by other force phenomena that had different (electrostatic, electromagnetic) rules of behavior. Accordingly, different sets of rules of behavior for presumably contained quantities of control activity were added to the set of physical rules that accomplished the nucleon accumulation and stability control process. The result is still a process of accumulation and conversion of free energy and matter (condensed energy?) into the smallest possible volume of space. The energy/matter equivalence value used in the theories was calculated by Einstein as being as if all matter in existence had a kinetic energy of motion equal to twice what it would have if it were moving with the velocity of light. Thus the nucleus is accumulated matter plus stored free kinetic energy of motion.WFPMWFPM (talk) 21:14, 2 October 2008 (UTC).WFPMWFPM (talk) 01:04, 3 October 2008 (UTC)WFPM (talk) 20:56, 13 October 2013 (UTC)


This page, like many of our science pages, suffers from the terrible flaw of being peppered with much scientific jargon that is not adequately explained. For example, observe the following paragraphs:

A heavy nucleus can contain hundreds of nucleons (neutrons and protons), which means that to some approximation it can be treated as a classical system, rather than a quantum-mechanical one. In the resulting liquid-drop model, the nucleus has an energy which arises partly from surface tension and partly from electrical repulsion of the protons. The liquid-drop model is able to reproduce many features of nuclei, including the general trend of binding energy with respect to mass number, as well as the phenomenon of nuclear fission.

Here, the editors do not make clear what a classical system is and what a quantum-mechanical one is. This would be bad enough, but the editors then go on to build off that confusing dichotomy, referring to the "resulting liquid-drop model." Since the reader has no idea what a classical or quantum-mechanical system is, the reader cannot even begin to grasp what a liquid-drop model might be, if the author had even bothered to explain what the fucking model was, or how it resulted from the ability to approximate a q/m system as a classical one.

Superimposed on this classical picture, however, are quantum-mechanical effects, which can be described using the nuclear shell model, developed in large part by Maria Goeppert-Mayer. Nuclei with certain numbers of neutrons and protons (the magic numbers 2, 8, 20, 50, 82, 126, ...) are particularly stable, because their shells are filled.

Here, the editors might have redeemed themselves by explaining something about quantum-mechanical effects. They at least mention a nuclear shell model, but then, infuriatingly, leave it at that. They do, however, go on to explain what this nuclear shell model implies, now leaving us totally in the dark, and chewing on ourselves in frustration.

Since some nuclei are more stable than others, it follows that energy can be released by nuclear reactions.

Finally, the editors continually make deductions that are not obvious to the reader, and don't bother to explain how they, or any physicist, arrived at them.

This is not a problem merely with this article: it exists in many others. Our articles are only useful as encyclopedia articles if they are penetrable to the layman.

As a conclusion to this general rant, could someone knowledgable about the physics of atomic nuclei clarify these points? Graft

I don't see a problem with using jargon. In fact, the jargon is an aid to understanding because the meanings are very precise. However, when jargon is used, there need to be links to articles explaining the concepts. I've added a bunch of links to this article, so it should be easier for a reader without any education in science to follow.

To use the existing example, if one doesn't know what surface tension is, then the liquid-drop model may not be obvious. Hence, a link to surface tension was needed.

Material replaced.

Helium was formed from hydrogen in nuclear reactions shortly after the Big Bang, while all the other elements in the universe were created in supernova explosions.

                                    Rednblu 13:23 20 Jul 2003 (UTC)

Many other places in this article need fixing, for example the last paragraph. Rednblu 13:49 20 Jul 2003 (UTC)

How big?[edit]

Please tell me what the size of a nucleus is? No comsmogony until basic material, cheers.

As it turns out, this depends on the element: A Hydrogen atom's nucleus (consisting of a single proton) is much much smaller than that of a Uranium-235 atom. Unknownmosquito 14:06, 7 August 2007 (UTC)

You might think of nuclear accumulation to be like marble accumulation with two different sets of approximately the same size marbles. For an example see Talk:Nuclear model .WFPMWFPM (talk) 01:13, 3 October 2008 (UTC)

Nuclear Fission[edit]

A changed the section a bit and removed the text about alpha and beta decay. I think it belongs in the Nuclear Decay section. Zarniwoot 00:35, 23 January 2006 (UTC)

Bohr atom[edit]

Since a Bohr atom is not a realistic model, can the picture go? There're lots of problems: Electrons as particles in orbits is wrong, the electrons are too big, and the space occupied by nucleus in the atom unrealistic. Olin 03:32, 29 March 2006 (UTC)

A semi-accurate depiction of the neutral helium-4 atom. The darkness of the electron cloud corresponds to the line-of-sight integral through the probability function of the two-electron 1s electron orbital. The inset nucleus magnified 150 times; it is schematic, showing two protons in red and two neutrons in blue. In reality, the nucleus is spherically symmetric.
The image I proposed for the atom article is available. Suggestions are still welcomed for improving it. The main problem, of course, is how to make an interesting picture of something that is spherically symmetric and essentially homogeneous. -- Xerxes 15:59, 29 March 2006 (UTC)

fm unit for size of nucleus[edit]

In the first paragraph it stats the size of the nucleus in the unit fm. Clicking on fm merely takes you to the disambiguation page for fm. Should it not take you to the actual page for the unit? Or perhaps the unit should be stated not in it's short form. I think it may be confusing to someone who is not a scientist. —The preceding unsigned comment was added by (talk) 21:57, 7 March 2007 (UTC).

Yup, links to disambiguation pages are stupid. Fixed. However, since it's defined in the page (10^-15 m), perhaps the link isn't needed at all? --Gmarsden 18:18, 8 March 2007 (UTC)

Inline template[edit]

The inline template at the head of the page was displaying a couple of columns of documentation text rather than nice little alert infobox about the article needing citation work. Not sure why this should be the case. I have removed it for now, but the article should still be tagged with the proper (or repaired) box. - (talk) 04:58, 7 June 2008 (UTC)


spherically symmetrical. What exactly does this mean? (talk) —Preceding comment was added at 02:38, 9 July 2008 (UTC)

It means that the function depends on radius only, and does not depend on angular coordinates at all. Which means in turn that you pass through exactly the same "scenery" at a given distance from the origin, no matter what direction you choose to take. SBHarris 02:50, 9 July 2008 (UTC)
Is there evidence for this spherical symmetry, or is it a theoretical supposition? --TraceyR (talk) 17:54, 22 August 2008 (UTC)
The article Nuclear physics states explicitly that "Nuclei are not all spherical. Some can exist with giant haloes. Whilst others can also exist in giant cigar or ring states, superdeformed by excessive spin". This would appear to contradict the above definition of spherically symmetrical. This inconsistency needs to be addressed. --TraceyR (talk) 20:26, 25 August 2008 (UTC)

OK, I have now corrected the image caption and deleted the incorrect statement that the (presumably any) nucleus is spherically symmetric. Dirac66 (talk) 00:07, 26 August 2008 (UTC)

Thanks. Interestingly, the description associated with the graphic in Commons states that spherical symmetry, while true for He, does not apply to more complicated nuclei - that bit got left out in the original caption here. --TraceyR (talk) 08:23, 26 August 2008 (UTC)

Propose we get rid of neutrino discussion[edit]

The history of the neutrino, its theory and detection (already the subject of many other articles), is really no more a part of the story of the atomic nucleus than (say) the same history for the electron or positron. I propose this stuff be deleted down to a single link to neutrino (where beta decay is mentioned). The history of the neutron, of course, is more germane, but all that neutrinos have going for them is that they initially were called neutrons (a bit of trivia that isn't even worth mentioning here, either, due to being confusing). But neutrinos don't really exist in the nucleus any more than electrons or gamma rays do. If you'd like me to, I'll be glad to make a first cut, here. SBHarris 03:04, 9 July 2008 (UTC)

Contents to be swapped with that of Nuclear Physics?[edit]

Compare Nuclear physics with Atomic nucleus. The contents of these two articles should be swapped! Nuclear physics is the field of research. Atomic nucleus is the object of research of this field. History, Modern nuclear physics and -topics should go into Nuclear Physics, because its the more general, background information and related to the definition of the research field. On the other hand, nuclear forces, nucleus models and info about neutron/protons should go into Atomic nucleus, as these are the details about the object of research. (As a comparison, on German Wikipedia, it is the way it should be: vs.

I'd be happy to implement the content swap, but as i'm new to Wikipedia, i wanted to discuss this first. (Hope this is the right place) Also note that Atomic nucleus is B grade while Nuclear physics is Starter. I'd also like to enhance the new Atomic nucleus (after swap) then.

Lars Ruoff (talk) 20:44, 23 July 2008 (UTC)

By golly, you are right that the two articles you note above should be basically switched in content, then cleaned up a bit. You certainly have my vote to do it. Be WP:BOLD. SBHarris 21:22, 2 October 2008 (UTC)

Problem above fixed[edit]

In absense of rabid comment, I have been WP:BOLD and moved a lot of stuff on the structure and composition of atomic nuclei to the atomic nucleus article, while moving a lot of stuff about nuclear physics that was sitting oddly in the atomic nucleus article, to its proper place in the nuclear physics article. I also removed some "personal physics theory" personal research POV-pushing (which had also been noted by another author) from the nuclear physics article. A nuclear physicist really needs to go through this stuff. The job is not done, but most of the big chunks are now where they belong, I think. SBHarris 18:32, 3 October 2008 (UTC)

O.k. I have a question. If the nucleus is made up of nucleons then how can it also be made up of protons and neutrons?? Dumb?? Yes. Bored?? No. Griffin10 —Preceding unsigned comment added by (talk) 23:25, 15 January 2009 (UTC)

"Nucleon" is a generic word for either a neutron or a proton. SBHarris 23:32, 15 January 2009 (UTC)

Figure caption[edit]

I find it rather unlikely that the figure caption is correct, which reads: A semi-accurate depiction of the helium atom. In the nucleus, the protons are in red and neutrons are in blue. First, I doubt the nucleons are neatly separated and arranged in a planar fashion. I also doubt that they are red and blue in color. I have modified the caption. Brews ohare (talk) 14:08, 17 October 2008 (UTC)

constant size?[edit]

"Although the size of the nucleus varies considerably according to the mass of the atom, the size of the entire atom is comparatively constant."

This is wrong. The size of the entire atom varies considerably according to its mass. Gakrivas (talk) 15:30, 11 March 2009 (UTC)

I think this sentence is anyway useles here. I remove it. Kopovoi (talk) 12:02, 12 March 2009 (UTC)

Removing an incorrect statement doesn't provide information. There is a source for atomic radii here (there are many other sources) showing the relative sizes - perhaps someone familiar with the subject could formulate something along the lines of "Although the size of the atomic nucleus varies considerably according to the number of nucleons and therefore the mass of the atom, the size of the entire atom varies considerabley less, ranging from x Angstrom (smallest element) to y Angstrom (largest element)." Something along those lines would give the reader a better idea of the absolute and relative atomic sizes. --TraceyR (talk) 15:48, 12 March 2009 (UTC)
I fully understand your concern and I did not delete the information because it was wrong. I mean the information unnecessary, because the very next paragraph is about atomic nucleus size. The article is about the nucleus, so I think that any explanations what is the atomic size, how you define it and how it depends on atomic number should be and are already in another article Atomic_radius which is linked from Atom article. I just wanted the header be clear and short. I thought it would be quick discussionless correction :-). Kopovoi (talk) 10:14, 13 March 2009 (UTC)

Dearth of sources[edit]

For an article of such significance there are very few in-line citations. I know that it's a major task, but there really should be more. For example, in the section on halo nuclei there's lots of fact but not a single reference. In fact, there are currently only seven references in the whole article! --TraceyR (talk) 22:35, 15 July 2009 (UTC)

comparing radius of nucleus to size of atom[edit]

The following sentence from the intro is confusing: "These dimensions are much smaller than the size of the atom itself by a factor of about 23,000 (uranium) to about 145,000 (hydrogen)." This compares the diameter of an atomic nucleus to the "size" of an atom. How is the size of an atom measured? Are we referring to radius, diameter, volume, what? Gary (talk) 18:52, 25 August 2009 (UTC)

Agreed. In fact, since the intro is supposed to summarise the salient points of the article body (does it in this case?) and since there doesn't seem to be a reference to back up the relative sizes (?) given, there's quite a bit of work to do. I have assumed that the relative sizes given refer to diameters, but without a cited source it's impossible to know. --TraceyR (talk) 19:57, 25 August 2009 (UTC)
They were originally referring to diameters (or radii). The numbers were simple divisions done by me, using atomic radii and nuclear radii. I suppose they are "original" but on the other hand, they are simple arithmetic ratios using basic data from atomic radius and atomic nucleus. The statement can be replaced by a single factor (about 100,000) as is usually done, but as you can see the ratio of atomic diameter to atomic nuclear diameter, varies by a factor of 5 or so from the lightest to heaviest atoms, so you lose quite a bit of information in assuming the oft-quoted (and probably easily referenced) statement that all atoms are roughly 100,000 times larger in diameter, than their nuclei. But feel free to change it in any way that makes you comfortable, as I can't defent it with a citation. SBHarris 00:52, 26 August 2009 (UTC)

Why the Nuclear Scientists Redirect ?[edit]

Why the redirect from Nuclear scientists??? I need a list of the most prominent nuclear scientists. I know in the 1950's some of them had the hairbrained idea that a series of sub continental shelf explosions should change the course of the golfstream and lead the warmer waters of the Gulf stream in another direction up along the east coast to make New York warmer in the winter among other things. It would be nice to have a list and list some of the major discussions and proponents of different ideas up through the post war period.

Nunamiut (talk) 03:11, 8 October 2010 (UTC)

Who is this Ivanenko bloke? As a non-expert I would have expected to see Chadwick's name here. If my man-in-the-street understanding is wrong, shouldn't the article tell me why it's wrong, not just mention a strange name? — Preceding unsigned comment added by (talk) 05:37, 6 June 2012 (UTC)

Stability of A = 3 Nuclei[edit]

In the article, it is explained that the "residual" strong force acts between any two nucleons whereas the electrostatic charge force pushes the protons apart. However, the nucleus of 2He3 is noted to be stable (with 2 protons), and the nucleus of 1H3 is not, and the decay mode is presumably a B- (electron) emission by one of the neutrons. How does that occurrence agree with the expressed attractive force theory?WFPM (talk) 02:17, 19 March 2011 (UTC)

The repulsive force between protons is just one of the factors that must be taken into account. The fact that neutrons are intrinsically heavier than protons is also important. for lighter nuclei the extra mass of neutrons is the more important factor because there are not too many protons packed in the nucleus to begin with. For larger nuclei the repulsive force between protons is more important hence the fact that heavier nuclei have many more neutrons than protons. Read liquid-drop model for a detailed discussion. Dauto (talk) 02:43, 19 March 2011 (UTC)
A neutron is more massive than a proton by 1293 KeV or so. If the neutron in tritium can change to a proton it has to emit a 511 keV beta, and that leaves 1293 - 411 = 410 keV to play with. Some has to go with the neutrino, but not much. The decay energy of 18.6 keV is very low, and the difference between 410 KeV and 18.8 KeV is mostly to make up for that proton-proton repulsion that now appears. How close do two protons need to be, to have their potential exceed 390 KeV = 6.24e-14 J? Well, divide by 9e9 and (1.6e-19)^2, invert to get radius, and obtain 3.7e-15 m = 3.7 fm. The charge radius for He-3 is 1.96 fm (larger than the 1.67 fm for He-4, where you get an extra neutron drawing things in) [1]. This means that the root mean square charge-diameter of a He-3 nucleus is about 4 fm, which is larger than the 3.7 fm we get from our missing neutron mass. Evidently the neutron spends more than its share of time in the middle and the two protons as far away from each other as possible, but these numbers are close enough to measured reality, that it's not outrageous. Perhaps in order to avoid each other, one proton in He-3 has to be promoted so it's no longer 1s and goes to 2s or whatever the next nuclear orbital is. That's certainly what I'd do if I was a second He-3 proton. How about you? SBHarris 02:50, 19 March 2011 (UTC)
That's highly unlikely. I think the protons remain both at the 1s state.Dauto (talk) 03:51, 19 March 2011 (UTC)

Well I've always wondered, and my Kaplan (page 512) says that the binding energy of 3H3 is greater (8.482mev) than that of 3He3 (7.711Mev) by (0.711Mev). And it attributes the lesser binding energy to the coulomb repulsion. And that would indicate the 3He3 nuclide to be the larger. And since a deuteron would repel a proton with a greater force than a neutron, it's more logical and more probable to accumulate an additional neutron, and the question then becomes as to why 1 of 2 nearby neutrons would want to become a proton.WFPM (talk) 04:25, 19 March 2011 (UTC) After all, the thing that's supposed to be unstable is the 3H3 nucleus with only 1 proton. Could it be that the nucleus is planar in structure and that the 2 protons have to repel each other in order to not come into rotational contact?

One of the neutrons wants to turn into a proton for the same reason that a free neutron wants to turn into a proton. It wants to shed its extra mass. I thought I had made that clear in my previous answer. Dauto (talk) 19:04, 19 March 2011 (UTC)

Good premise that leaves us with a concept of a deuteron plus loose extra sort of stabilized extra neutron as 3H3. And after that we have the problem of the two protons, and a still possible planar structure. And then we need an additional neutron to get to 2He4, so there must be some of them available. So it can't be all protons.WFPM (talk) 20:03, 19 March 2011 (UTC)

External References[edit]

The following two external references are home-spun articles containing sections promoting the controversial concept of 'hormesis' due to ionizing radiation. There is reason to suspect external link abuse.

Pcp071098 (talk) 09:10, 16 March 2013 (UTC)