Talk:Bohr model

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[edit] Ryderberg section

I remember reading that one of the reasons why the Bohr model was rapidly accepted was because he predicted the Ryderberg (sp?) constant for hydrogen. I'm wondering if the text should be modified in that section to imply this. Meaning maybe deriving the Bohr model equation such that its solved for the constant in that section? And then showing the empirically measured numbers plugged in and getting the same number? 128.163.110.72 13:12, 10 January 2007 (UTC)

I've added a couple of sentences making this even more clear in both the beginning section and the Rydberg section. The only thing lacking is derivation of the Rydberg constant in anything other than electron volts. Do you think that's really necessary? If you read the Wiki on the Rydberg constant (which is linked) that's all done for you, over and over. SBHarris 18:39, 10 January 2007 (UTC)

[edit] Recent editing

I did some serious editing of the first couple of paragraphs. My qualifications are that I have a PhD in chemistry and took a year of quantum mechanics.I also was a high school chemistry eacher for many years. First, I tried to clarify the model to represent what Bohr suggested in 1913--he thought that electrons traveled in circular orbits. About 10 yrs later de Brogile suggested that electron motion may have wave like properties but this is not what Bohr proposed in 1913 and so to say in the first paragraph that electrons travel in waves as seen in an earlier edition I think is confusing. I also tried to explain some of the history in a little more detail. I’m pretty sure everything I wrote is correct, and I really hope I did not offend anyone with me edits. I’ll probably work on this page later (I have a regular job). Pez2

>I have a regular job

What, and the rest of us don't? JabberWok 20:33, 29 November 2006 (UTC)

I was just tring to be witty. Sorry if I offended anyonePez2 00:07, 30 November 2006 (UTC)

I thought it was funny! I definitely don't have a regular job. JabberWok 01:06, 30 November 2006 (UTC)

[edit] Comments regarding previous versions of the page

The second to last paragraph needs work. QM does not treat electrons as waves. It just says that the probability of measuring an electron is given by the the magnitude of a wave. The "absurdly wrong" doesn't belong there either, QM doesn make judgements :) AN

Comment dates from Sept. 2002. --Christopher Thomas 21:19, 20 Jun 2005 (UTC)

[edit] Obsolete or not?

At the moment Geocentric model is in the Category:Obsolete scientific theories while Bohr atom is not. Both are now commonly held to be ontologically deficient but both are still useful for computation and pedagogy. Surely we should be consistent but which way? Cutler 20:44, July 11, 2005 (UTC)

Agree. Newton's law of gravity is an obsolete theory also, in that sense. Einstein said the most honorable fate for any scientific theory is to have it live on as a limiting case of something more general. Balmer's theory was generalized by Rydberg. Bohr explained Rydberg's constant. Moseley generalized Lyman-alpha to other elements. Schroedinger explained why these attempts gave some answers in some cases but not others. So it goes. In looking at sciene I'm truly astonished at how often scientists have been able to guess more or less correct physical math relationships on the basis of bad or totally imcomplete theories and assumptions. Or theories with just plain bad assumptions. Sometimes assumptions are recovered from just screwing around with equations. Planck didn't write down his black body equations knowing his constant. He graphed out the results and dimensionalized the equations and messed around with them until there wasn't anything left BUT one extra funny fudge factor, and that WAS where the constant came from. The old relativistic but non wave-mechanical Bohr-Sommerfield theory came up with the fine structure constant first, not Dirac. And second and even third quantum numbers for electrons were known before Schroedinger. When the full QM treatment for alpha scattering by gold was worked out, it gave the same result as good old Rutherford's newtonian picture (and this happens ONLY when the potential drops as 1/r, not with any other field, so Rutherford lucked out. The universe is a weird place. We owe all these prior scientists more respect, since of course we (with our cool modern theories) are still in the same place THEY were. We can hope for no better but to be obsolete one day in the same ways THEY were. SBHarris 17:12, 9 December 2006 (UTC)

[edit] How do electrons instantaneously change orbital shells?

The subject explains the question. How do electrons change orbital shells in this model? To my knowledge, nobody knows this, and such a lack of knowledge is important to mention. If there is an answer on the page, it has escaped me.

—The preceding unsigned comment was added by 24.153.226.112 (talk • contribs) .

I'm not sure this question is meaningful. As with any other model, it is an approximation of reality. In this case, one of the approximations made is that the transition is instantaneous. That is simply part of the model.

A more realistic model would describe the transition (change in state) in terms of an interaction between the electron and virtual photons, and give uncertainty in the transition time which could be thought of as a duration, but that too is an approximation to reality. At some level in any model, you'll get to a stage where interactions happen by magic (or rather, are assumed to be a fundamental building block of the model).

To give a contrived example, take the old physics joke that ends with "first assume a spherical horse of uniform density". Asking "how does this model say horses become uniform spheres" is turning things backwards - the point of the model is to make thinking about horses easier by starting with the assumption that they already are. Similarly, the Bohr model assumes that transitions are instantaneous as an axiom.

--Christopher Thomas 21:19, 11 November 2005 (UTC)

[edit] Here is another formula to calculate the energy levels.

where,

E_n is the energy level

E_r is the rest energy of the electron

α is the fine structure constant

n is the principal quantum number.

GoldenBoar 02:16, 17 December 2005 (UTC)

[edit] And a formula to calculate the velocity.

where,

v is the velocity of the electron

c is the speed of light in a vacuum

α is the fine structure constant

n is the energy level.

GoldenBoar 02:16, 17 December 2005 (UTC)

[edit] Math Markup Language

Can we please update the markup language to reflect the actual representation of the equations? —The preceding unsigned comment was added by Mross462 (talk • contribs) on 05:28, 22 August 2006.

I'm not sure what you mean by this. The markup used for the equations is LaTeX, which is pretty standard. --Christopher Thomas 14:25, 22 August 2006 (UTC)

[edit] Intro image debate

On 01/20/07, User:WillowW reverted my image (below left) for her image (below right), per “please use the correct ratio of radii (1:4:9) and only one arrowhead; color is nice, too; you could wait for me to SVG this older Figure on Monday”.

Sadi Carnot’s image of the Bohr model.

Willow’s image of the Bohr model.

JabberWok’s image of the Bohr model.

Enoch lau’s image of the Bohr model.

I disagree with this. First, according to what I’ve read of Bohr’s 1913 paper, there was no “color” in his model. Second, in Willow’s model the nucleus is bigger than the electron, which is not the case in Bohr's paper. Third, the photon waves are zig-zaggy, rather than wave-like. Fourth, although Bohr says that “the diameter of the orbit of the electron in the different stationary states is proportional to τ²”, he calculated different radii using a formula and gets diameter values such as 1.6E-6 cm (for τ = 12), or 1.2E-5 cm (for τ = 33), etc., for different series. Fifth, a double arrow, as I've seen used elsewhere, allows for both emission and absorption discussion, and is thus a more versatile image. Sixth, as far as I know, Bohr never actually drew his model out? Here's a Google image link to more Bohr models. Please comment. --Sadi Carnot 07:26, 23 January 2007 (UTC)

I would propose a combination of the above images. Certainly, Bohr did not use colors in his paper, that is something of this time, but that does not mean we cannot use it, on the contrary. Drawing the sizes of electrons and the nucleus in one image on scale is going to be a difficult task anyway, but anything reasonable would suffice, ratios of the diameters of the orbits should be according to Bohr's proposition. I agree with the form of the wave and the double-headed arrow. The sixth argument is a bit silly, sorry. Hope this helps. --Dirk Beetstra ^{T C} 09:23, 23 January 2007 (UTC)

Hi, I hope I didn't ruffle any feathers; if I did, I'm sorry. Here's what I think happened. I made my image back in September for the Photon article and added it here as well. Jabberwok quite rightly replaced my PNG image with an SVG image, also in color, on the 10th (two weeks ago). Then, Sadi replaced JabberWok's image with the monochromatic one above. I offered to replace my PNG image with a SVG version, but maybe it's time to make a new and better hybrid. Any volunteers?

The main issue I was trying to raise is that formula for the radius is a quadratic function of n, which is the only parameter (quantum number) in Bohr's model. I think we should strive to make the Figure quantitatively accurate, not merely qualitatively correct. Depending on the plotting program (I used Xfig), it's not hard to draw radii in the proper 1:4:9 ratio; I just counted grid squares, but one could also write a computer program to do it.

I recognize that the nucleus is too large in my figure, but I wanted it to be visible. The nucleus will be too big in every possible image, since it's roughly 100,000 times smaller than the electronic orbitals, right? (~10^-15 meters versus ~10^-10) Since we have to forgo scale-accuracy here, we should just add a comment to the caption that the nucleus is actually much smaller than shown.

Personally, I like bright colors, but I understand that not everyone does. However, since our goal here is to write as clear an article as possible, and not to reproduce Bohr's original paper with historical accuracy, it seems OK to use color. You might not have noticed, but the color of the emitted photon (656 nm) agrees roughly with the color shown (red); that's why I chose the 3→2 Balmer transition.

The wave could definitely be better in mine; it was the best I could do by hand. :( The other two are definitely better.

I understand the purpose of the double-headed arrow, but I'm not sure that lay-readers will. Speaking for myself, I think it would be better to show one direction of arrowhead, either spontaneous emission (my fave) or absorption. The flow of events in spontaneous emission is easy to understand: the electron drops down in energy and the photon leaves. To have double arrowheads on the electronic jump and the photon seems like it would be confusing to lay-readers, trying to pack too much into one image. It's often best to explain one thing well, and then extend to other topics. Willow 12:27, 23 January 2007 (UTC)

I think the best attribute of Willow's image is the 1:4:9 radii. The others are inaccurate in this regard and this is important. I would prefer a nucleus which is only slightly larger than Sadi Carnot’s. Color is good especially if used in the caption to point things out. I prefer JabberWok's font on the levels and his wave and double headed arrow. I like the size of willow's electrons. There is also something to be said for the clarity of choosing only emission and perhaps having one electron grayed out or a circle indicating that it used to be there. Yes, it is less versatile. --Nick Y. 19:56, 23 January 2007 (UTC)

I second all of Nick Y.'s comments. The ratios of the radii are important -- that is the key quantitative feature of Bohr's model that feeds directly into the experimental agreement with hydrogen spectroscopy. I also like the idea of showing one of the electrons grayed out or an open circle to indicate that it has jumped down to a different orbit. HEL 20:48, 23 January 2007 (UTC)

[edit] Uploaded new image

Sadi Carnot's (2nd) image of the Bohr model.

PAR’s image of the Bohr model. Gray lines, not dotted. Single arrows illustrate emission electron jump and emission photon. Orbits in 1:4:9 proportion. Nucleus too large.

Owing to the above suggestions, I uploaded a new image, adjusted the orbits (1:4:9), used a little color, added charges, left one electron an open circle and the other closed, used one arrow head, and set the sizes of the nucleus (10^-15 meters) and electron (10^-18 meters) based on current views (source: Frank Close's 2004 Particle Physics). Do we all like this one? I'll try to adjust the font size up. Any further suggestions? --Sadi Carnot 23:55, 23 January 2007 (UTC)

Hi Sadi, it's looking pretty good! :) Here are a few comments/suggestions, as you asked.

• I'm beginning to understand why a monochrome version might be better than a colored one. For example, readers who photocopy the article or print it out won't need a special printer to understand it. I'm glad, though, that you kept the photon red, close to 656 nm. The sinusoidal part looks great as well!

• The full-scale image is easy to understand, but the reduction to ~300 pixels makes it more difficult to make out certain features, such as the text, the thin dashed lines for the orbitals and the open vs. the closed circles. Such high-resolution features will only get worse if the article is photocopied after printing. So I would make everything one notch thicker/bigger in the full-scale version: slightly larger circles, larger font, coarser dashes (JabberWok's dashes look good to my eyes), thicker orbital lines, etc. so that's it's easy to "read" at small scale.

• If you can fit it, I would put +Ze near the nucleus and -e near the electron to indicate the charges. That's useful for integrating the Figure with the formulae.

• Along the same lines, perhaps use a capital E of ΔE for energy? I'm worried that the Greek ε might look too similar to the Roman e for charge, and readers might get confused. Also, that way, we can tie in with the formulae on Photon and Bohr model.

• This is trivial point of aesthetics, but the "jump" arrow looks too bent? Could it be a little more direct?

• Oh, and finally, the image should be SVG, not PNG or JPG, as suggested somewhere in the Manual of Style, if I recall correctly. SVG is clearly the format of choice for a schematic diagram like this one.

Thanks for taking the time to work on making the Figure as good as possible! :) Willow 11:49, 24 January 2007 (UTC)

Willow, all good points, especially the +Ze and -e suggestion; Bohr specifically states that the positive charge of the nucleus, which he says is “exceedingly small” compared to the linear dimensions of the atom, is equal to the total negative charge of the electrons. Hence, we should use a ( +Ze / -e ) format in the diagram; except Bohr used (+E and - e) for the nuclear and electron charge, if this makes a difference? Also, I think the Delta Δ symbol is misleading; Bohr didn’t use Deltas, Heisenberg was using them in 1930, but Bohr used W_τ2 - W_τ1 = hν as his energy change formula. The Greek ε was that originally used by Planck in 1900. I agree that the image should look good at 200px. The electron “jump” should probably either be a “wave”, per possibly analogy with Maxwell’s 1873 electromagnetic theory, or a “straight line”, per Alfred Mayer’s 1878 floating magnet experiment (which the ringed electron model is actually based on). Lastly, sorry to say, I don’t have an SVG option presently; I’ll have to get one some day. --Sadi Carnot 18:02, 24 January 2007 (UTC)

I come over here looking for a fight and everyone seems to have worked things out :P I'll try to be useful all the same, even if I am basically happy with Willow's images or with Sadi's second attempt.

• I would also prefer ΔE instead of ε to refer to energy difference in this article which is likely to be read by non-specialists. I would also prefer an italic h for the Planck constant.
• I think that including charges would over-complicate the figure: we can't put everything in there, and we already have to compromise on the size of the nucleus (roughly 10⁻¹⁵ m, as Willow states) and that of the electron (your preferred Deity might know, but I don't and probably can't). The relation between energy change and nuclear charge is something whioch should be developed in the article text.
• I would prefer a straight line between the Bohr states, as we cannot really depict the complexity of the transition (and Bohr himself certainly couldn't).
• SVG would be the best format in an ideal world, but we can worry about that later: contributions are welcome in any wiki-accepted format, as the hardest part is to think of a good graphic, not to do the format conversion.

Congrats and thanks to all who have helped on this one. Physchim62 (talk) 17:00, 24 January 2007 (UTC)

Thanks for commenting Physchim62; it's hard to stir up a fight with Willow, she always seems to pacify the situation somehow? As per above, I don't think the Greek Delta Δ should be used. I do think the electron and the nucleus should be different sized per Bohr's comment that the nucleus is "exceedingly small" compared to the size of the atom. Par's recent image is good, only we should use charges and not have the Delta. I'll work on this more next week; unless, that is, someone else uploads a new image? --Sadi Carnot 18:02, 24 January 2007 (UTC)

I'm in favor of using the delta, since each electron has a particular energy above ground and its the difference in the energy of the upper and lower level that is converted to photon energy. In other words the above energy is E₃-E₂ which I think should be written ΔE.

I am having SVG problems too. I use Adobe Illustrator which can save an SVG file, but it is not compatible with Wikipedia, so I convert to a pixel picture and save as PNG. We definitely need an SVG file, because you cannot convert from PNG to SVG. (SVG to PNG, yes) If anybody has any ideas for my problem, please let me know. Also, if anyone wants to play with my version, I have it saved in PDF format, which is vector based, so you wouldn't have to construct an SVG file from scratch. I can email it if needed. PAR 22:06, 24 January 2007 (UTC)

For the time being, I used added charges to PAR's image. It seems good for now. Thanks: --Sadi Carnot 05:35, 26 January 2007 (UTC)