Talk:Molecular orbital theory

Simplify!

Cann somebody make this article so that anyone who does not have a backround in quantum theory and advanced math can understand it? Unfortunatly this goes for many science-related articles. They need to stop using terms that would only be known by people who probably already know the theory.

--Lophoole 00:42, 12 October 2007 (UTC)[reply]

I've simplified many math/science articles, putting them into laymen's terms, only to see my changes redacted. It's an unfortunate aspect of Wikipedia: technicality in math/science articles trumps readability, and the concept of 'redundancy' varies widely (one person's 'redundancy' is another person's clarity).

Br77rino (talk) 00:27, 5 December 2011 (UTC)[reply]

Yeah, I'm currently studying this in Organic Chem II, and what we have here reads like the Voynich Manuscript. I guarantee this is useful to absolutely _nobody_ who doesn't already consider it elementary. My professor doesn't even know what the heck is going on on this page. If had any idea how to start, I'd do it myself. 68.196.9.112 (talk) 03:07, 6 March 2012 (UTC)[reply]

Wishlist

Here is a little wishlist I have...maybe someone has an idea of how to implement this:

Take CH₄ and show how "sp³ hybridization" comes about from MO theory. In particular, highlight the fact that the MOs are one- and threefold degenerate, which from a superficial point of view, is contrary to the 4-fold degeneracy suggested by the hybridization picture. --HappyCamper 05:45, 7 January 2007 (UTC)[reply]

The hybrids are non-canonical MOs, that is, they are NOT eigenfunctions/eigenvectors of the Fock operator/matrix. Hybrids can be constructed by linear combination of a- and t-symmetry MOs, which have different orbital energies. Hence energies of hybrids are undefined. A remark of this type could be included in the article.--P.wormer 00:33, 18 March 2007 (UTC)[reply]

Query

Does this article have anything to add to molecular orbital?, candidate for merge in my view, what you are looking for in a qualititative way is represented in MO diagram but this article fails to provide a link. Also see my discussion with Smokefoot on this topic here V8rik 18:12, 7 January 2007 (UTC)[reply]

I am against merging. Molecular orbital theory, molecular orbital, and MO diagram are each their own topics. In your conversation with Smokefoot, as an example, you use the term “MO theory” as though this was common knowledge; yet until I started this page (a work-in-progress) there was nothing in WP that defined what MO theory was. The term MO theory is used all over WP; a redirect to molecular orbital doesn’t explain anything … everyone already knows what a molecular orbital is. The 2004 McGraw-Hill Concise Encyclopedia of Chemistry has a four-page section on "molecular orbital theory." If there is anything that needs to be merged or added to this article it is this section: Chemical bond#Molecular orbital theory; but I want, however, to make sure it is correct before I do so.

By the way, this article is almost brand new. Please give me some credit for trying to get it going. There are whole books and chapters written on specifically "molecular orbital theory". Also, aren’t you against mergers? You have a whole philosophy about this on your User page. Anyways, I am presently trying to build this article, bit by bit, so to show the contrast to that of valence bond theory. --Sadi Carnot 00:44, 8 January 2007 (UTC)[reply]

Hi Sadi Carnot! I am being grumpy again and please do continue with your good work. Yes I do maintain an anti-merge platform (not many supporters though) but I do occasionally merge. I will follow this page with interest. The point I am trying to make that in my view we can only get ahead in this Branch of theoretical chemistry if we at least introduce methane and also benzene MO treatment (more detail less overview). Also good point on the chemical bond article, the MO theory section there is too long and better placed here V8rik 18:22, 8 January 2007 (UTC)[reply]

V8rik, yes methane and benzene are good examples to have in the article. On your vote, I’ll do a quick merge of the some the MO material in the chemical bonding article. I apologize that I haven’t put any current basic molecular orbital theory into the article, but my current reading interest is on the “history of molecular orbital theory” (pre-1950s), i.e. how it came to be and whose ideas and shoulders it is built on. I’m sure I’ll chip in more later on the basics of MO theory (after I read a few more books on it), but for the present maybe you as well as others will help by adding a basic outline on current MO theory? --Sadi Carnot 03:46, 9 January 2007 (UTC)[reply]

I don't think the article needs to be merged, but as it it right now it says much about the early history of the theory but very little about the theory itself. The details about the MO theory are scattered in many articles; perhaps this one could serve as a starting point in the future, but in any case it would help to link to all of the relevant articles. Some examples of articles containing what you would find in a book about MO theory:

A good book on the topic, although a bit dated now, is Ab Initio Molecular Orbital Theory by Warren J. Hehre, Leo Radom, P. V. Schleyer, and John Pople. Wiley, 1986. Itub 14:59, 10 January 2007 (UTC)[reply]

Timeline

There is a lot of good work in the timeline, but most of if it is part of the early history of all of quantum mechanics, atomic physics, and nuclear physics. I would probably start the timeline of MO theory around 1926 and move the rest to another article on the history of quantum mechanics, but maybe that's just me. :) Itub 18:26, 8 January 2007 (UTC)[reply]

Itup, thanks for the comments and the related links. The book is a little too pricy ($150-used, $215-new) for me. The history of quantum mechanics needs to be a whole new article by itself. I was just looking at the Quantum mechanics#History section the other day and I was thinking about starting that page and moving much of that section there. Starting at a certain year, for either topic, however is a bad idea; it pre-assumes that the originator "thought" up the whole idea all by themselves. Most people, for example, have no idea that the concept of the "quantum" was actually derived and based the study of Boltzmann's entropy equation S = klogW (1872), i.e. that the derived roots of quantum mechanics are based on thermodynamics. --Sadi Carnot 03:46, 9 January 2007 (UTC)[reply]

For a history of quantum mechanics, I wouldn't object with starting with the cathode rays or even earlier. My reluctance to begin the history of MO theory that early is not because I think it was all created overnight, but just to avoid too much duplication, since MO theory is just a part of quantum mechanics and shares all the early history with QM. If we were writing a book on the MO theory, I wouldn't object either, because a book is much more self-contained than a Wikipedia article; however, here we can link very easily to other articles. You can mention the early history in an extremely condensed form and link to a more detailed article. Itub 16:35, 9 January 2007 (UTC)[reply]

Yes, I agree with you on the book point, but I'm not certain the QM and MO theory share "exactly" the same historical paths; certainly their is a lot of overlap. My point is that some people may not really care about reading a full account of quantum mechanics, and a lot of unrelated math. Thus, my long term goal is to eventually write two separate branch-off articles: History of molecular orbital theory and History of quantum mechanics. I'm sure I can write them both in time, we'll see? Also, there are dozens of articles that have historical origins to Planck's "quantum" energy units, but there's no need to merge them all together, we can have a separate history article for all of them, each with their own peculiarities. Another note is that my reading focus for these weeks is specifically molecular orbital theory, thus I try to contribute to only what I am reading about that week. So once this page gets too long, I'll move most of the history section to its own page. --Sadi Carnot 00:57, 10 January 2007 (UTC)[reply]

I agree with Itub's 8 January contribution at the top of what I have just made a new section. There is no need for history before 1926 as MO theory is quite meaningless without the Schrodinger equation. Maybe it can go somewhere else. A time line that deals with MO and VB as this one does, should perhaps go in quantum chemistry. It should not be here, as VB and MO theories are different. They are similar only in that they are both approximate solutions of the Schrodinger equation, and this article is about the MO approximation, not both. I suggest we have already got the history in its own section so the timeline table should go. It could be usefull in a broader "History of XXX" article. but I'm not sure what "XXX" should be. --Bduke 03:34, 10 January 2007 (UTC)[reply]

There you go Bduke, no more timeline. I’m just going to make a very strong personal note that this is the second time (here and at the valence bond article) that you have had problem with my sourced history contributions. --Sadi Carnot 07:31, 10 January 2007 (UTC)[reply]

I'm sorry you take it personally. I'm not opposed to history; far from it. However, history has to be relevant and focused in a science article. It is not just everything that has had some impact on the subject from way way back, however well sourced. I am happy to work with you in putting the timeline table into a new article on History of quantum chemistry. I actually know more of the history than most quantum chemists and have a colleague who knows even more. I have also lived through 50 years of it. What do you say? --Bduke 07:54, 10 January 2007 (UTC)[reply]

Ligand group orbitals

This idea should probably be somewhere too...just to register the idea for now. --HappyCamper 12:44, 9 January 2007 (UTC)[reply]

Image

Hello - we used to have this image on the article, but I checked the actual orbitals of this Methane, and they do not look too much like this, so I've removed it for now until we can find a better replacement. --HappyCamper 19:17, 11 January 2007 (UTC)[reply]

In **MO theory**, the shape of one molecular orbital of methane *CH₄*, as determined by the molecular orbital wavefunction, is a mathematical combination of five atomic orbitals: one s-orbital on the carbon atom and four s-orbitals on the four hydrogen atoms. There are *three* other molecular orbitals which are triply degenerate. These symmetries can be determined by considering the character table for T_d symmetry which the molecule of methane has.

Notational questions

1. In text \psi and \chi are small Greek, as is usual for orbitals (one-electron functions). In equation capital Greek is used:

\Psi _{j}=\sum _{i=m}^{n}c_{ij}\mathrm {X} _{i}

.

Why?

2. What is lower limit m? --P.wormer 00:20, 18 March 2007 (UTC)[reply]

You are right. I've fixed it. --Bduke 00:43, 18 March 2007 (UTC)[reply]

Overview - garbage

The following is found in the overview and is garbage:"Conversely, an antibonding orbital will more closely resemble the higher energy atomic basis.[7] Electrons in non-bonding orbitals tend to be in deep orbitals (nearly atomic orbitals) associated almost entirely with one nucleus or the other, and thus they spend equal time within as they do between nuclei. These electrons neither contribute to nor detract from bond strength and thus are best described as lone pairs." A lone pair is in the nucleus??? It is "deep" ??? the AB-Orbital resembles the basis?? Garbage!Abitslow (talk) 20:25, 21 May 2014 (UTC)[reply]

Concur, see tag added today, and this is only the obvious of many more subtle misfiring cylinders here. Leprof 7272 (talk) 07:36, 3 March 2015 (UTC)[reply]

Expert attention requested

Came here to link to this article, from other applied wikpedia articles on reactivity. Simply cannot use the article in the state that it is in. All the touchups, technically and otherwise, are lipstick on a pig. Paste this into Word, do a word count, and then go look for a comparable book chapter or review article of similar length and see how the topic is covered in that professional venue. Then come back here and see if there is anything to salvage. Bottom line, I concur with the Feb 2014 tag that the very large block of narrowly and naively sourced material added in Nov 2013 was without proper depth of understanding or scope for it to be done well. This article needs a major overhaul, and we cannot link to it, or recommend it, until such is done. Le Prof Leprof 7272 (talk) 07:36, 3 March 2015 (UTC)[reply]

Indeed, the article is a complete mess. It is a shame, because around 8 years ago it was much better. Brian Duke, who is a theoretical chemist of note, contributed significantly in the beginning of this article. Apparently he gave up on it. This could well be exemplary for the future of Wikipedia: decent articles are screwed up by nitwits during the course of time. Experts get fed up and stop caring.--P.wormer (talk) 16:15, 3 March 2015 (UTC)[reply]

I will see if I can have a look at it sometime, but I am very busy with other stuff. I am doing little other than checking my watchlist. --Bduke (Discussion) 20:52, 3 March 2015 (UTC)[reply]

Bd, perhaps you can provide a guiding bibliography, and help others develop an outline for a replacement article? I envision a good starting point would be to simply cover the information appearing in the relevant entry or entries in P.W. Atkins' Quanta, expanding it with any further sections decided useful (e.g., history and such), then "diluting" that body of substantial content down to that of an entry level college text (choosing a couple of these, as examples to compare). If I were giving this as a senior chem student teaching project, that is how I might guide them to see the effort's scope. BUT, Bd's guidance and advice would trump anything I can say here. Leprof 7272 (talk) 01:54, 4 March 2015 (UTC)[reply]

Here is a look at Atkins' Quanta: [1], accessed this moment. Leprof 7272 (talk) 02:07, 4 March 2015 (UTC)[reply]

With Wikipedia's version control, there is no reason to let an article moulder. If there is consensus that the article has deteriorated in the past couple of years and seems too much effort to incrementally fix, one approach would be to revert to an earlier, known solid, version of the article. The first step in this approach would be to identify a good earlier version to revert to. Do any of you three have opinions on this? Leprof 7272 seems to indicate that the version prior to the big additions in Nov 2013 might be a solid version to revert to. I am far from an expert on MO theory, so don't feel qualified to judge the best version myself. --Mark viking (talk) 21:25, 3 March 2015 (UTC)[reply]

Returning to an earlier version is a possibility that occurred to me also. But first let me ask Leprof 7272 and P.wormer (and others who may agree with them) - are there actual errors and misstatements in the article which can be corrected, or is the problem merely the informal nature of many of the sources as the tags seem to suggest? And would it really be easier to rewrite the added material from scratch, as opposed to substituting better references and correcting some errors? Dirac66 (talk) 22:10, 3 March 2015 (UTC)[reply]

Thanks to Bd for responding, and to all the rest of you for prompt attention. My vote is clearly to scrap, and start from near to scratch (saving solid, sourced prose when practical). This said because PChem and MO theory are frought with such subtlety at times, that to try to second guess any author, even the finest, can be a challenge. To try it with an earlier novice editor drawing from online course materials, and so whose founding perspective is undeclared and diffuse—is simply a waste of time. There is no baby to save in this [post-Nov 2013] bathwater. (My view.) I leave it in your collective able hands, and will only add citations and comments as text/examples touch on levels of theory applied to day-to-day OChem operations (e.g., Ian Fleming's nice "MOs and Organic Chemical Reactions"). If time permits, make sure the explanations here are copacetic with the one appearing at Oxygen, an article that I have given up on (other than to see the nice Jack Barrett 2002 homonuclear diatomic MO diagram and explanation remain in). One point from experience—perhaps take the time, among you, to agree on a rough outline, then begin, one section at a time, first with absent sections, then with one-by-one section replacements (rather than gutting the thing all at once). I think a stepwise process according to a plan will be more harmonious among you, and less disruptive to those on the sideline (and so less likely to run into unnecessary politics as you proceed). Note, I will return with voice to support whatever Bd, you and the others decide. Cheers, and thanks again. Leprof 7272 (talk) 01:35, 4 March 2015 (UTC)[reply]

I've tried to rescue the article by removing most of the edit material made by the IP on 24 November 2013 and transferring the added material not currently covered in our articles to the respective articles, such as molecular orbital diagram, ligand field theory, etc. Not sure if that would help? --Officer781 (talk) 10:23, 26 March 2015 (UTC)[reply]

Good job. I have now deleted the tags about the unreliable sources which you have removed. There is of course always room for additional sources and further improvement, but at least the sources now included are acceptable. Dirac66 (talk) 23:13, 28 March 2015 (UTC)[reply]

Article is much better now.--P.wormer (talk) 09:46, 29 March 2015 (UTC)[reply]

Erroneous statement?

The claim: "If the electrons tend to be present in a molecular orbital in which they spend more time elsewhere than between the nuclei, the orbital will function as an anti-bonding orbital and will actually weaken the bond." seems wrong to me. For example, the "pi" bonds in benzene have zero probability density on the line connecting the carbon atoms, but are not anti-bonding. Could an expert fix this, or if it's correct explain it better? Ma-Ma-Max Headroom (talk) 20:11, 17 January 2016 (UTC)[reply]

I agree that is wrong, but it is also wrong in a more fundamental way. Using the same language, even in bonding orbitals, as well as antibonding orbitals, electrons spend more time near the nucleus than between the nuclei. The electron density always peaks at nuclei unless the nucleus is a node due to symmetry. Bonding only makes small difference to the electron density between the nuclei. I will have a look at the article. --Bduke (Discussion) 20:50, 17 January 2016 (UTC)[reply]

I have made some edits, which I think are more correct. --Bduke (Discussion) 21:01, 17 January 2016 (UTC)[reply]

I have removed the words than elsewhere, which no longer fit in the sentence after BDuke's edits. Also since Ma-Ma-Max Headroom mentioned pi bonds, I realized that between the nuclei suggested on the axis between two nuclei, and replaced it by the in the region between two nuclei. What I really mean is anywhere in the region between the two planes which are perpendicular to the internuclear axis and which pass through the two nuclei, but I think that wording would be far too clumsy for the article. Dirac66 (talk) 21:50, 17 January 2016 (UTC)[reply]

Last paragraph

I have removed the last paragraph added by an anon editor. It is entirely speculation based on articles which do not appear to have been properly refereed. It is not appropriate in this article at this time, but may be later if it is supported by other papers that are refereed. --Bduke (talk) 21:57, 7 March 2020 (UTC)[reply]

Merger proposal

Hi all, I have proposed merging the problematic article Electronic structure into Electronic band structure. That gathered little discussion and did not pass. A new proposal was put forward to merge the page here instead. Please leave a comment if you have an opinion on the merger or the future of the Electronic structure article in general. The discussion link is on Electronic band structure still, discuss here. Thank you. Footlessmouse (talk) 22:10, 10 October 2020 (UTC)[reply]

Merging here makes no sense, as molecular orbital theory is only one part of the theory of electronic structure in molecules. I would prefer that it be merged into Quantum chemistry, but that article needs work. --Bduke (talk) 22:57, 10 October 2020 (UTC)[reply]