Latest comment: 11 years ago24 comments10 people in discussion
I came across this truly awful structure of KH2PO4. Further, the Smiles formula proved to be invalid in Accelerys Draw so I could not easily correct it.
Unfortunately this is one example of goodness knows how many dreadful structures. In particular it shows, in VB terms, one canonical form of a resonance hybrid of the anion. Personally, I would prefer to see a delocalized MO structure (of the anion in this case). What about the crystal structure?
Simple structures like this one should be planar representations of the 3-D structure. Surely, the "flat" representation is long past its sell-by date? Can we form a little group to address this issue of general significance? Petergans (talk) 09:36, 19 November 2013 (UTC)
The structure at least conveys connectivity. For many readers a single resonance structure probably is more useful than something showing delocalization. As we all known these discrete things dont even exist because the materials are polymers with very strong cation-anion interactions, but one worries that readers simply cannot deal with that fact, so we dumb it down to show the polyatomic ions. If yo want to see "stupid" (to me), look at sodium chloride where two spheres are presented, but I guess these convey relative ionic radii.
The bad news is that coordinates for these purely inorganic materials reside in the Karlsruhe crystallographic database, which is less accessible than Cambridge one. The good news is that many simple inorganic materials are isostructural, such that once one image is found, it can be applied to articles on several articles.
As is often the case with inorganic compounds; it's crystal structure has polymorphs. Although these are further compicated by its ferroelectric character ( 10.1107/S0365110X53000776 seems an ok start point). I agree that the structure should show some 3D character (although I've seen people get confused over dashed bonds: is it delocalisation or stereochemistry?) but I'd be wary about going too far. We're trying to explain things here: an image of an infinate 3D ionic polymer is very pretty (and very accurate) but it's of little use to someone who just wants to know what the molecule looks like. Project Osprey (talk) 15:32, 19 November 2013 (UTC)
Regarding molecular structures, there are two issues here, geometry and bonding. On geometry the structure of the anion is near tetrahedral, tout court. Also, independently of bonding theory, the two P-O bonds are equivalent and have the same length (ignoring solid-state effects). Please, please, please, no dumbing down if that means presenting incorrect information such as, in this case, a P-O bond and a P=O bond instead of two equivalent bonds. Petergans (talk) 16:49, 19 November 2013 (UTC)
Thats's great! I would leave out the K+ altogether and make it clear both in the text and the caption that this is the (idealized) structure of the anion Showing the bond lengths and angles, like in sulfuryl chloride, would be even better, but that can wait. Now, what about phosphate? In the article the space-filling structure shows a regular tetrahedron, but the VB structure does not! See also Potassium phosphate and diphosphate and related structures... Petergans (talk) 11:01, 20 November 2013 (UTC)
One cannot omit the K+. The article is about potassium compound, not the anion. The image is fine for an article on phosphates, but not potassium compounds. We've been through this before. The arguments are motivated by noble goals, but we get stuck with these practical issues. The thing to get is the crystal structure of salt.
Hi, folks. I just stumbled upon this conversation and thought I would add in my opinion, for what it's worth. While I certainly appreciate the noble goal of presenting only "correct" information, I should point out that it is more easily said than done. I don't know of any scientific theory can be regarded as the truly correct way that nature operates. Every time we try to provide a physical interpretation of natural phenomena (including something as widespread as molecular structure) we inherently mess something up by making it "incorrect."
Some of the best descriptors of nature are purely mathematical models that offer no intuitive physical insight. For instance, why even bother drawing molecular structures that have the potential to be flawed when we can just list out the nuclear coordinates? I would argue that the coordinates are not as intuitively pleasing as a molecular structure drawn with implied connectivity.
Even if we were to use a structure that showed delocalized molecular orbitals (as was suggested above) we would have to keep in mind that molecular orbitals are derived from a one-electron picture of molecules and are far from what actually happens in a molecule (e.g. electron correlation). That is not to say that molecular orbital theory isn't useful because it serves as a tool that can be used to understand and predict many phenomona. We sacrifice some rigor in pursuit of gaining physical intuition. So if we're OK with using molecular orbital theory, why can't we be OK with one particular resonance structure?
OK, so what's my point? I don't think it does much good to fuss over such issues. No matter what we put up here, it will eventually be found to be flawed in some regard. As we pursue the least flawed explanations, we leave our audience behind us in the dust. The fact is, the vast majority of folks looking at a structure of KH2PO4 will be people with no more background than an introductory course in general chemistry. Whether one P-O bond is represented as implied as longer than as... is of negligible significance for these folks. If flat canonical forms of hybrid structures are so bad, then why are they so widely used for introducing molecular structure? The answer is because it is only one piece of the puzzle. You have to start somewhere and you can always add in the extra stuff (typically more complicated) at a later time. For any folks where this difference will matter, they will learn more about the "actual" structure by linking to other pages (e.g. the page on molecular geometry).
We need to strike a balance between accessibility and rigor. I believe that focusing on these issues puts us way out of balance on the side of rigor. I am trying to pull the conversation back toward accessibility. JCMPC (talk) 02:18, 23 November 2013 (UTC)
This is not a question of rigour, but of fact. The two P-O bond lengths are the same, as are the two P-OH bond lengths. Showing one canonical form gives a false impression of the physical structure. Would you show the structure of nitrate as O2N=O? I don't think so. P.S. there is now a crystal structure in potassium monophosphate and a link to the structure of the anion. Petergans (talk) 08:49, 23 November 2013 (UTC)
I agree with JCMPC. Being factually correct is often less important than being easy to understand. The reality is, even for people very familiar with structural chemistry, it is easier and more practically useful to think about and draw simplified structures in the first instance, then refine the model with more nuanced and detailed descriptions as necessary. For example, it is easier to determine the oxidation state of phosphorus in phosphate at a glance from the localised Lewis structure than from a delocalised diagram. It is also easier to make an analogy with molecules with more localised bonding such as triphenyl phosphate.
Depictions of phosphate of varying complexity and detail
Localised bonding. Easiest to understand for beginners.
Localised bonding, but indication of stereochemistry.
Localised bonding, but delocalisation indicated by resonance structures.
Indication of delocalisation and stereochemistry.
Space-filling model, shows 3D shape without distraction of bonding detail - but sometimes hard to see all atoms.
Ball-and-stick model, showing full 3D structure and dashed bonds indicating delocalisation and equal P-O bond lengths.
Full 3D model of the crystal structure - lots of information but complicated at a glance. Tells you lots about the whole but less about the components.
In most WP articles, the first paragraph begins with a simple description of the topic and more detailed discussion is left to later sections. The same principle should probably apply to images of chemical structure: the simplest structural representation first (even if it's an oversimplification), followed by more accurate but more complicated corrections to the oversimplified model later on. I am happy to help locate crystal structures and make images of any substances whose Wikipedia articles you think would benefit from it. --Ben (talk) 12:50, 24 November 2013 (UTC)
I agree that the use of images such as File:Potassium monophosphate.png is perfectly acceptable, particularly in the introduction of an article, and that more complex descriptions of chemical structure can be detailed and illustrated deeper in the article if necessary. The widespread use of this image across multiple wikis, and of similar images throughout our chemistry articles, is evidence that this view is the current consensus. Depictions such as this are entirely conventional in professional chemistry. Referring to images that show one canonical form of a resonance hybrid as incorrect is just pedantic. (How often do you see aromatics drawn as anything but alternating single and double bonds in chemistry journals?) Defying convention for the sake of pedantry does a disservice to our readers. -- Ed (Edgar181) 13:34, 24 November 2013 (UTC)
Hate to be pedantic ;-) .. but why do we regard the K-O 'bond' as ionic, and the H-O 'bond's as covalent in the image? In the crystal structure I presume that the H's and the K's are all shared 'between' the surrounding PO4-units, and in solution the H's and K's likely swim around a bit more (depending on the solvent; ions are likely solvated and different equilibria take place). Calling rock-salt 'Na+Cl-', 'NaCl' or 'Na-Cl' is similarly confusing and unrealistic.
That being said, the first image is quite acceptable, the more 'real' cases (solid state structure and situation in solution) can be described later and should show more realistic images. Keep it simple (s.....) does it best as start. --Dirk BeetstraTC13:58, 24 November 2013 (UTC)
I am horrified by the statement above "Being factually correct is often less important than being easy to understand.". if Wikipedia has things which are factually incorrect what use is it? What's the point of "understanding" something if the facts about it are wrong? What we have to do is make more effort to explain things which are not immediately obvious. Like, for example, why the structure of phosphate 2nd. from the left above, apparently lacks tetrahedral symmetry, while its space-filling structure apparently does show tetrahedral symmetry. This is not pedantry - readers may be confused by such apparent contradictions. It follows that, to be consistent, what is good for PO43- is good for other phosphate ions. Petergans (talk) 19:50, 24 November 2013 (UTC)
FWIW, I am not horrified by "Being factually correct is often less important than being easy to understand." Since the meaning is that factual correctness could exclude a large fraction of our readership. Experts realize that almost every structural representation is misleading in some way. The single resonance structure of phosphate seems fine to me. The connectivity is there. The charge is there. The idea that P-O interaction is more than a single bond is there. To a trained eye, the tetrahedral geometry is there. Confession: I actually like carbonate shown with distinct single and double bonds. Like Edgar181 said, even benzene rings are depicted incorrectly throughout Wikipedia. But we need to be careful. In that context it is healthy for us to review which compromises we make and which ones we should avoid. --Smokefoot (talk) 20:20, 24 November 2013 (UTC)
Images such as File:Potassium monophosphate.png are conventional representations of chemical structure. The information conveyed is not dependent solely through what the viewer sees, but also through the reader's understanding of the conventions which are used to present complex issues of chemical bonding in a shorthand way. If our readers are confused by such representations (and I'm not sure they are), we need to do a better job of teaching how to interpret them rather trying to use more complex, non-conventional ways of depicting chemical structures. ChemNerd (talk) 20:35, 24 November 2013 (UTC)
I agree that it essential to keep it simple in the beginning. Start too complicated and you will lose readers. Absolute correctness becomes irrelevant if no one reads it. All of these depictions represent models of varying degree of completeness and accuracy. All models are wrong, some are useful. A simple model, if it assists in understanding, is useful. Boghog (talk) 20:49, 24 November 2013 (UTC)
In my response above, I was not trying to imply that being factual is more or less important than being factually correct, just that we need to strike a balance between the two. Also, while one could argue that not being correct means that we are the purveyors of false information, I would counter-argue by echoing Boghog's statement that "all models are wrong, some are useful." And, by models, I mean to imply models based on some level of physical intuition. In many cases, the more physically intuitive a model, the less "true" it becomes. We could restrict ourselves to developing models that are "true," but then we wouldn't gain much, if any, physical insight. Without physical insight, we lose a lot of the predictive power of science. For example, we could use the Virial equation of state to describe how the pressure of a gas is related to volume and temperature. Using this approach, it is possible to reproduce experimental data perfectly, but is almost impossible to extract any insightful information about "why" the gas behaves as it does. Instead, we could use a van der Waals equation of state to describe the same gas. This approach would not only give a comparatively poor reproduction of experimental data but would also be suggest completely unphysical behavior (e.g. increase in pressure as the volume is decreased). However, using a van der Waals equation of state would provide insight to molecular properties such as intermolecular forces and molecular size. While not technically true, I don't know anyone who would argue that the van der Waals equation of state shouldn't ever be used, referred to, or taught (or even the ideal gas law for that matter!). The same arguments can be made for molecular structure. While one flat canonical resonance structure isn't "true", it certainly has its merits, both scientifically and pedagogically. I don't mind the use of more rigorous representations as long as the central point of what is trying to be conveyed isn't lost in the detail. Furthermore, as was mentioned in some of the comments posted above, there is the question of the context in which a compound is being discussed. While this thread started with the example of KH2PO4, I believe that the argument is more general. I would hate to see lots of other incredibly useful structures eliminated just because of a few of the finer points of their interpretation. JCMPC (talk) 01:24, 25 November 2013 (UTC)
Let's not get carried away. By factual I mean something established by observation. In the case of phosphates this means a tetrahedral geometry around the P atom, established by countless crystal structure determinations. When it comes to bonding, both elementary VB and MO theories are approximations. Therefore saying something like "The electronic structure is shown, by valence bond theory, to be such and such" is correct and admits the intrinsic approximations. Where necessary an electronic structure can be described as a resonance hybrid. One canonical form of a set has no place in a chem box; a description of electronic structure, mentioning or showing resonance, (see, for example, nitrate) belongs in the text. Petergans (talk) 09:41, 25 November 2013 (UTC)
That -> is also not established by observation, we draw the 4 rings flat, where, in fact, the 6-membered rings are all in a chair-conformation, and 3-substituted carbon of the 'isopropyl-y' end of the tail is not in the same plane as the 3 carbons it is connected to (and adding to this, the molecule is flexible and not 'frozen' in conformation, especially the tail).
Depicting atoms 'flat' or (as drawn for cholesterol) 'trigonal-pyramidal' in stead of the more correct tetrahedral for every carbon atom is a very normal way of depicting - it is certainly not past its sell-by date. I can agree that for KH2PO4 drawing a 'tetrahedral' variety is easy and not making it complicated, but it is far from 'truly awful'.
I would be very careful with using crystal structures as 'true' depictions of how a molecule looks like - they are, often, skewed by crystal packing and/or interactions between neighbouring molecules in the lattice, polymorphism (and it is 'frozen' - the crystal structure of cholesterol may show the tail consistently in the same ordering, but in solution/liquid/gas phase that is different). Crystal structures may not even show the most stable conformation of a molecule! Moreover, we have problems with the compounds that are not found in the solid state. It is about as correct as a gas-phase minimized structure coming from a DFT calculation (I would (very wild) guess that in a minimized structure the KH2PO4 unit then has the potassium bound to 2 oxygens, and two OH-groups, resulting in the O-P-O angle of the potassium bound-oxygens to be smaller than expected for tetrahedral, and the angle between the other two oxygens too wide, and 2 different P-O bond lengths - or a K+ in close proximity of a H2PO4- in a spiro-like conformation, now having a distorted tetrahedral conformation on P - or a K+ in close proximity of a P(=O)2(-OH)2 anion, which is again not tetrahedral and has different P-O bond lenghts - your guess is as good as mine).
Regarding the chemboxes, we can not depict all 'correct' structures (what is the correct structure of a sugar again?), but we should at least chose one which conveys what we are, within reason, talking about - and one canonical form of the molecule is then certainly what c/should be there. --Dirk BeetstraTC11:06, 25 November 2013 (UTC)
Sorry to disagree. The cholesterol structure is accepted as a typical representation on the plane (i.e. paper) of a 3-D structure of an organic molecule, and the arrangement of single and double bonds is reasonable. Moreover, the 4 rings present an almost flat profile... What was truly awful was the diagram showing K+ and H2PO4-. You won't find a diagram like that in any modern text-book on inorganic chemistry.
The substantial point that I'm trying to make is that there is an essential distinction between physical structure, based on experimental observations, and bonding, based on theory. Bonding theory should support the physical structure, not appear to contradict it. Petergans (talk) 14:12, 25 November 2013 (UTC)
There is no doubt that the concept of resonance in VB theory is a hard one to grasp. I remember as a student being completely flummoxed when the bonding in diborane was described as involving bond, no-bond resonance. That's why I prefer MO theory when dealing with delocalization. Delocalization is often inescapable in inorganic chemistry, as in the carbonate, nitrite, nitrate, phosphate and sulphate ions just to mention a few simple cases. Petergans (talk) 14:12, 25 November 2013 (UTC)
And that is where I think that the flat representation, as a first approximate, is not thát bad (though I agree it here could be better easily without making it too complicated, and you have my support to change it into a better image showing at least the tetrahedral environment of the P). By the way, resonance is quite a common theme in organic chemistry as well, though still everyone is writing an amide as 'R2N-C(=O)-R, that structure is not backed up by experimental evidence - it is quite funny there that the flat representation is actually correct :-), whereas the (accepted) flat representation in the cholesterol is not. --Dirk BeetstraTC11:19, 26 November 2013 (UTC)
I am pleased to see the ap-pauli-ng structures changed. There only merit was in highlighting the valence/oxidation number of the central P. How much d orbital contribution is still moot, but as with sulfate the theoretical concensus, from my reading of it, is that its "just a little but not a lot". The phosphate article is where the bonding of all these ions could be discussed in depth. Axiosaurus (talk) 12:50, 26 November 2013 (UTC)
sorry typo spoilt an appalling appauling (bad) joke but seriously pi bonding in tetrahedral phosphate and sulfate is of minor importance - Pauling went over board with the electroneutrality principle and we are left with his legacy of a phosphate pi bond which is misinterpreted as being like an N=O bond. A simple Lewis structure with nice octets is probably closer to the polar reality. Phosphate is the place to put a neutral description of the various theories- I did something similar for sulfate years ago.Axiosaurus (talk) 16:46, 26 November 2013 (UTC)
New editor quick review
Latest comment: 11 years ago4 comments4 people in discussion
A lot of this editors work early this morning was not very good, looking like someone trying out editing for the first time. Sort of random thoughts or remarks were inserted into various articles. This editor has however produced a large article Stereoelectronic Effect, which is a topic that is important but I dont follow. My usual complaint with these new giant articles applies - over reliance on primary sources, vs WP:SECONDARY. My guess is that there are many articles within WIkipedia that discuss stereoelectronics, perhaps in a more fragmented way. Notice that he started Stereoelectronic Effect because Electronic effect already existed, which shows the tendency of an inexperienced or undisciplined editor, who creates new (marginal) content vs improving existing content. --Smokefoot (talk) 20:01, 24 November 2013 (UTC)
Even IUPAC knows this term.[1] And as a fellow organiker I've often heard and used it in relation to all sorts of structure/reactivity ideas that have orbital-geometry as the underlying principle. But if the article doesn't include that authoritative source as part of its definition, that's a problem. And if the article is using some other meaning, that's a serious problem. DMacks (talk) 15:40, 27 November 2013 (UTC)
More about structures
Latest comment: 11 years ago4 comments3 people in discussion
Following on from comments by user:axiosaurus above, I draw attention to these three structures and the inconsistency between them. The three ions are isoelectrionic and isostructural. The bonding can be described with sp3 hybridization on the central atom. There is no need to show either double bonds or delocalization. What, if anything, is gained by showing those aspects? Why show 3 bonding schemes for isoelectronic species? In the case of sulphate, does the bond length shown apply to all 4 S-O bonds? In response to Axiosuarus's point about d orbitals, may I point out that with regular tetrahedral symmetry the bonding can be described with a mixture of sp3 and sd3 hybridization, which may confer some partial double-bond character on the A-O bonds and still keeps the regular tetrahedral geometry with 4 A-O bonds of the same length. Petergans (talk) 14:55, 27 November 2013 (UTC)
I would argue that all three of those structures are incorrect in some ways. To my knowledge, I don't believe that there is a single way of depicting a compound in a way that simultaneously correctly represents connectivity, symmetry, and the activity of valence electrons. For example, as drawn, the last structure of perchlorate does not use any wedges or dashes, so how can we imply it's three dimensional structure is tetrahedral? I would argue that we know it's tetrahedral because we know what the experimental data reveal, not because of that particular depiction. Sure, the electrons are shown to be symmetrically shared among the four bonds, but that could also apply if perchlorate happened to be square planar. The rough orientation of the four bonds is drawn as though wedges and dashes were used, so you may imply 3D geometry that way, but, I only recognized that because my eye is trained. To a novice, those four bonds may as well be in the same plane. Similarly, the first two structures (phosphate and sulfate) do indicate a rough 3D structure. While it does not imply tetrahedral symmetry, it does imply a roughly tetrahedral orientation. Additionally, these two structures don't do a good job at showing the equal distribution of valence electrons among all four bonds (as you noted); however, they do display formal charge in a much more convenient way than if they were depicted using the same format as perchlorate. While it can be argued that formal charge is not "real," it is a useful tool for depicting asymmetrical charge distribution along a bond. While all three structures are isoelectronic and isostructural, their charge distributions will be far from the same. (I know that they are all non-polar molecules due to symmetry. I refer to the degree of polarization of each individual bond.) While I understand that other resonance forms and delocalization of electrons occur on phosphate and sulfate, a novice would not. But I don't see how this is any different than perchlorate. You're just trading one type of "correctness" for another. JCMPC (talk) 20:00, 27 November 2013 (UTC)
If no image is perfect, but we have a range to choose from, why not just use several images? Chembox code allows for that and it's already used on many pages. Project Osprey (talk) 23:48, 27 November 2013 (UTC)
As long as the images don't get too cluttered, I don't see why several would be bad. Currently, the phosphate page has three such images. If space filling models don't make sense for something like dihydrogen phosphate, maybe one crystal structure (which is currently posted) and one Lewis structure? JCMPC (talk) 04:53, 28 November 2013 (UTC)
IUPAC names
Latest comment: 11 years ago1 comment1 person in discussion
Latest comment: 10 years ago1 comment1 person in discussion
Hello, does anyone know the origin of suffixes and prefixes in chemsitry?
The wikt:-one suffix in organic chemistry? Our wiktionary article says it is Probably Ancient Greek -όνη (-onē), but I thought it was from ketone by dropping "ket" ?
The wikt:hydro- prefix seems to be conflating the version concerning water with the version concerning hydrogen on wiktionary. Isn't the version concerning hydrogen originating as hydrogen dropping "gen" ?
If what I'm think is the right formation, then there's very many errors on Wiktionary needing correction.
Latest comment: 10 years ago2 comments1 person in discussion
Dear chemists: This old abandoned Afc draft will soon be deleted as a stale draft unless someone cares to rescue it. Is this a notable topic? —Anne Delong (talk) 17:37, 6 December 2013 (UTC)
The periodic table should follow IUPAC recommendations. http://iupac.org/publications/ci/2004/2601/2_holden.html The long form is a simple expansion of the short form. This means putting La under Y, Ac under La, Ce and the other lanthanides after La, Th and the other actinides after Ac. Group 4 (Ti,Zr,Hf) then goes in a column after the lathanides and actinides. Lu is not under anything. Lr is under Lu. There should be a gap of 24 columns between groups 2 and 13 in the first 2 rows, that is, between Be and B, and Mg and Al. In Row 4, beginning with K, there will be a gap of 14 columns between Sc and Ti. In row 5, beginning with Rb, there will be similar a gap between Y and Zr. Row 6 should be continuous, Cs, Ba, La, Ce...Lu, Hf...Hg,Tl ...Rn. Likewise row 7. Petergans (talk) 17:28, 28 November 2013 (UTC)
I do not see any statement on their website stating that IUPAC recommends the Sc/Y/La/Ac version, or indeed any version, though according to Sandbh IUPAC has asked Scerri to form a working group to make the change to Sc/Y/Lu/Lr official. If anything all their periodic tables on their website show the Sc/Y/*/** version. In fact they've placed the group 3 question up for discussion ([2]), and the opening statement by Scerri is heavily in favour of Sc/Y/Lu/Lr. Double sharp (talk) 03:35, 29 November 2013 (UTC)
OK. Another authoritative source would be "Chemistry of the Elements" by Greenwood and Earnshaw. Inside the front cover group 3 is explicitly shown as Sc, Y, La, Ac. "Inorganic Chemistry" by Housecroft and Sharpe shows group 3 as Sc,Y,La-Lu.Ac-Lr. Shriver and Atkin, "Inorganic Chemistry" shows the same. My old (5th Edn.) of Cotton and Wilkinson, "Advanced Inorganic Chemistry" does not have a PT, but includes Sc and Y in the chapter on lanthanides.
Everyone knows that the * in Sc/Y/*/** means La and following elements. Lu is shown as a lanthanide in all short form PT that I know of. Please let's not waste any more time on this futile discussion: there is no single classification that will satisfy all criteria. The compromise that I have suggested above, is one that will be generally acceptable. Petergans (talk) 09:09, 29 November 2013 (UTC)
Yes, the asterisks refer to all the lanthanides and actinides. It do not privilege La and Ac, or Lu and Lr, above the other lanthanides and actinides. Counting it as a support for Sc/Y/La/Ac is in my view a mistake.
Cotton & Wilkinson's classification is the basis for the proposed recategorization. Evidently, they found Sc and Y to be much more closely allied with the lanthanides than with the transition metals (where they are usually placed). Hence I argued that it is supported by reliable sources and additionally makes sense to classify Sc, Y, and the lanthanides jointly as rare earth metals (a name still in use!).
Lu as a lanthanide is not something either of us dispute: chemically, it surely is one. But so is La, and somehow that is sometimes taken out of the lanthanide series and placed as a transition metal, although physically speaking, Lu has much more in common with the transition metals than La. Taking La as a transition metal – I don't think it's used that widely; even in books that do use it, I'm quite certain that La would still be discussed again with the other lanthanides, at least as a comparison. And it also works OK if you do that for Lu instead. Double sharp (talk) 10:08, 29 November 2013 (UTC)
Any PT version whatsoever can be displayed in a specialist article where its basis is explained. For example the unusual versions in periodic table#Alternative layouts. Chembox should contain a standard layout preferably the uncontroversial short-form, as in the IUPAC article.. Petergans (talk) 14:49, 29 November 2013 (UTC)
Sc/Y/Lu/Lr short-form is just as uncontroversial as the IUPAC one (if not less so). It is also gaining quite a lot of ground and is by no means an unusual version. Double sharp (talk) 01:28, 30 November 2013 (UTC)
Please supply support for your point of view by citing sources in peer-reviewed journals or text-books. C&W state "Lanthanides plus yttrium are commonly called rare earths. ... Scandium ... is not, therefore, truly a rare earth but it is convenient to discuss its chemistry in this chapter". No mention of Lu being other than a lanthanide. Petergans (talk) 11:08, 30 November 2013 (UTC)
Again, putting Lu under Y does not mean that Lu is not a lanthanide, just as putting La under Y does not mean that La is not a lanthanide. Why is double categorization permissible in the case of La and absolutely prohibited in the case of Lu?
And on C & W: evidently, it is more convenient to them to discuss Sc's chemistry with that of Y and the lanthanides, than with the transition metals. Sc and Y are not always classified as transition metals; even when they are, the references in question almost always include words implying that they are atypical transition metals (and that they have close links to the lanthanides). A classification of Sc, Y, and the lanthanides as rare earth metals sidesteps the whole issue. It is also worth noting that IUPAC explicitly defines (p. 51) the term "rare earth metal" to mean Sc, Y, and the lanthanides. Sc is not too atypical anyway for a rare earth metal; it's kind of like a mini-version of Lu.
Yes, but nowhere does IUPAC appear to state that this is the recommended version, despite using it. 15LaAc also creates problems for the long version, for it places all the lanthanides and actinides under Sc and Y, making hugely elongated Sc and Y cells if you take it literally! Double sharp (talk) 01:39, 1 December 2013 (UTC)
Sandbh here. My confusion about all of this goes like so:
IUPAC does not take a position on the composition of group 3.
Despite semi-popular belief, IUPAC does not take a position on what should be regarded as the correct periodic table (Leigh 2009; Scerri 2012).
I've seen books that show (a) Sc/Y/La/Ac; (b) Sc/Y/*/*; and (c) Sc/Y/Lu/Lr.
When I ask about why the differences, it turns out that type (a) appears to have originated in the 1940s based on electronic configurations and the concept of the differentiating electron, and not much else—see, however, Lavelle (2008; 2009) who still advocates Sc/Y/La/Ac on this basis; type (b) effectively treats all 15 lanthanides as members of group 3, seemingly at odds with the basic periodic table principle of one element per periodic table place (Scerri 2012); type (c) was used by a number of chemists in the 1920's and 30's on the basis that the chemical properties of Y, and Sc to a lesser extent, were closer to Lu—until what these 'old' chemists knew was discarded in favour of more 'noveaux' electronic configuration arguments, in the 1940s.
Jensen reviewed the question of which elements make up group 3, in 1982. He concluded Sc/Y/Lu/Lr, on the basis of physics and chemistry-based evidence. Emsley (2001, p. 527), on the weight of evidence, depicted Sc/Y/Lu/Lr and noted that, '…Jensen [had] argued cogently for this change to be made to periodic tables…'. Other authors followed suit: Lewis & Evans (2001); Barrett (2002); Ball (2004); Atkins & Jones (2007); Oxtoby, Gillis & Campion (2008); Jensen (2009; responding to Lavelle); Brown et al. (2009). In 2012, Scerri re-reviewed the situation in Chemistry International, the IUPAC news magazine, and confirmed the validity of Sc/Y/Lu/Lr.
If we can only show one periodic table in our element box then it could presumably be based on the least confusing version, resting on the most reliable evidence-based sources, with variations acknowledged as and where appropriate.
It is relevant to note that Scerri has been asked by IUPAC to form a working party with a view to making Sc/Y/Lu/Lr official.
Atkins PW & Jones L 2007, Chemical principles: The quest for insight, 4th ed., WH Freeman, New York, ISBN0716773554
Ball P 2004, The elements: A very short introduction, Oxford University, Oxford, ISBN0192840991
Barrett J 2002, Atomic structure and periodicity, John Wiley & Sons, Hoboken, New Jersey, ISBN0471444685
Brown TL, LeMay HE, Bursten BE, Murphy CJ & Woodward P 2009, Chemistry: The central science, 11th ed., Pearson Education, Upper Saddle River, New Jersey, ISBN0132358484
Emsley J 2001, Nature's building blocks: An A–Z guide to the elements, Oxford University Press, Oxford, ISBN0198503415
Jensen WB 1982, 'The positions of lanthanum (actinium) and lutetium (lawrencium) in the periodic table', Journal of Chemical Education, vol. 59, no. 8. pp. 634–636, doi:10.1021/ed059p634
—— 2009, 'Misapplying the periodic law,', Journal of Chemical Education, vol. 86, no. 10, p. 1186, doi:10.1021/ed086p1186
Lavelle L 2008, 'Lanthanum (La) and actinium (Ac) should remain in the d-block', Journal of Chemical Education, vol. 85, no. 11, p. 1482, doi:10.1021/ed085p1482
—— 2009, 'Response to "Misapplying the Periodic Law"', Journal of Chemical Education, vol. 86, no. 10, p. 1187, doi:10.1021/ed086p1187
This is all very interesting and shows how different criteria lead to different layouts. We have to choose one for the chembox. My suggestion is that we follow the major inorganic text books (also Skoog/West/Holler/Crouch "Analytical Chemistry") showing group 3 as Sc, Y, La, Ac. Lu in the lanthanide series, not under anything. Wulfsberg's Inorganic Chemistry appears to be the sole exception among modern texts. Accepting this proposal will cause the least confusion for WP readers. Likewise,the short-form representation is the one with which students will be most familiar. Petergans (talk) 10:38, 1 December 2013 (UTC)
, at some time in the future IUPAC makes a different recommendation the situation may be reviewed.Petergans (talk) 10:38, 1 December 2013 (UTC)
But Sc/Y/La/Ac is physically and chemically not ideal. Already our recategorization of the nonmetals is highly unusual (show me a book where At is rightfully not called a halogen; there problably are some, but I don't think they're in the majority)! And IUPAC has not made a recommendation.
(Sandbh, you mentioned that IUPAC asked Scerri to form a working group with the view of making Sc/Y/Lu/Lr official; reference please? Because that's quite a good rationale.) Double sharp (talk) 12:07, 1 December 2013 (UTC)
There is no "ideal" PT. Each has its own merits, but that's not the point. This is Wikipedia, which addresses a very wide audience. My proposal is simply to adopt, for the chembox, a form that is in widespread use today, a form which is de facto recognized by IUPAC. This will be helpful for the wider readership. Other forms may be discussed in the article periodic table which is devoted to that sort of thing. Petergans (talk) 14:30, 1 December 2013 (UTC)
Sc/Y/La/Ac is not even de facto recognized by IUPAC; all their periodic tables on their site show Sc/Y/*/**, evidently a way of keeping neutral (as they do not take an official position on the composition of group 3). Such a choice gives serious problems for the long-form; what are Sc and Y over? And I don't really see any merits of Sc/Y/La/Ac, by the way: in Jensen's paper he doesn't list any but the differentiating electron (which is now an argument in favour of Sc/Y/Lu/Lr with newer electron configurations!) Double sharp (talk) 02:12, 2 December 2013 (UTC)
Periodic table distributed by Inorganica Chimica Acta
The table labelled "IUPAC Periodic Table of the Elements" (http://www.iupac.org/fileadmin/user_upload/news/IUPAC_Periodic_Table-1May13.pdf) version dated 1 May 2013, does not have Sc/Y/*/**. Under Y it has "57-71 Lanthanoids". This means that 57La is under Y.This is clear and unambiguous. In the Sc/Y/*/** form, the * means "Lanthanides go here" and there is also a * before La in the separated row to indicate this. This is clearly shown in my pocket PT at right where a and b are written instead of * and ** Petergans (talk) 09:35, 2 December 2013 (UTC)
Thanks for posting the graphically pleasing image. I have a comment and a question if you will please.
To clear up the relevance of the supposed IUPAC periodic table, the following extract is from Leigh (2009) who at the time of writing was a member of the Chemical Nomenclature and Structure Representation Division (IUPAC Division VIII). He was discussing IUPAC and periodic tables:
'Figure 1 is based upon the periodic table that appears on the IUPAC website, though nowhere is it stated that that version is "approved." In fact, IUPAC has not approved any specific form of the periodic table, and an IUPAC-approved form does not exist, though even members of IUPAC themselves have published diagrams titled "IUPAC Periodic Table of the Elements." However, the only specific recommendation IUPAC has made concerning the periodic table covers the Group numbering of 1–18.'
My question follows. I look at the IUPAC periodic table and see '57-71' in the box under Y. From this, I cannot tell which element it is, La or Lu that is supposed to be the period 6 member of group 3, unless I picture a 32-column wide version of this table, in which case La would presumably follows Ba, then Ce to Yb, and then Lu would fall under Y. However, you say, 'This [the IUPAC periodic table] means that 57 La is under Y. This is clear and unambiguous.' I do not understand how this format is 'clear and unambiguous. What greater say does it confer to La over Lu? It still seems ambiguous to me.
Perhaps we can agree that there should be just one element that is the period 6 member of group 3, whether that is either La or Lu. Sandbh (talk) 10:35, 2 December 2013 (UTC)
Furthermore, how do you spin out the IUPAC table into a 32-column format? If we take the placement of "57-71" in the box under Y literally, it could even mean that Sc and Y are stretched cells fitting over all the lanthanides!? That would be very odd. And this doesn't privilege La over Lu, or indeed Lu over La, in any way I can see. Double sharp (talk) 12:10, 2 December 2013 (UTC)
The crucial difference is electronic structure. For the chemically important trivalent ions, Sc3+ = [Ar], Y3+ = [Kr], La3+ = [Xe]. That's why they can be classified as being in the same group. The Lu3+ = [Xe]4f14 ion does not have a noble gas electronic structure. This has little relevance to its chemical behaviour, but is a critical distinction. In fact the resemblance of Lu chemistry to that of Y can be seen as a diagonal relationship, brought about by the similarity in ionic radii resulting from the lanthanide contraction. It is comparable to the Zr/Hf relationship which is why some people put Y/Lu in the same group in spite of the difference in electronic structure.
My main concern is for the chembox. It does not show the element names so the structure needs to be one that can be easily understood because it is familiar. That means it should be in the short form. The form with 14 boxes for the lanthanides is preferable because the number of f electrons in the M3+ ion corresponds to the column number within the lanthanide row.
For the long form a good case can be made for both Y/La and Y/Lu. A discussion of this point belongs in the periodic table article.
I'm confused by your first argument. The tetravalent ions are important for Ti4+ = [Ar], Zr4+ = [Kr], Ce4+ = [Xe], Th4+ = [Rn]. Why are they not classified in the same group, and Hf4+ = [Xe]4f14 inserted into group 4 without the noble gas electronic structure? Why are Al and Ga in group 13 when Al3+ = [Ne] and Ga3+ = [Ar]3d10? Are those diagonal relationships too? (And are you saying that the relationship between period 5 transition metals and their period 6 congeners is solely from the similarity in ionic radii?! I thought they had the same common oxidation states too, and were really congeners unlike Li and Mg?!!?)
As for the chembox, the main issue with the short table is this: it's not obvious if Sc/Y/La/Ac or Sc/Y/Lu/Lr is being used without the symbols. In the long form, this is clear: you either glue group 3 to group 2 (Sc/Y/La/Ac) or group 4 (Sc/Y/Lu/Lr).
(Also: the ions work just as well with Sc/Y/Lu/Lr. You just have to start counting from 0 instead of 1! That's also more consistent with what you get if you tally the electron configurations of the monopositive ions across the periodic table; you start with 0 electrons in the outer shell in the alkali metals...) Double sharp (talk) 01:42, 3 December 2013 (UTC)
Jeeeeeeeeee, @Double sharp and Sandbh:, why has there developed a second thread here in the same topic? What am I supposed to think or do? Why was this not steered to WT:ELEM? What a chaos. Sorry, Petergans, my talk below must seem strange now. What a letdown. -DePiep (talk) 19:16, 8 December 2013 (UTC)
chembox
Latest comment: 10 years ago18 comments4 people in discussion
Will someone please explain
Why, when and by whom was the {{chembox}} replaced by {{infobox}} on all element pages.
Was this change an agreed policy?
How can one change the content of a template {{infobox element}}?
I am seriously concerned about the use, in chembox/infobox, of a long-form periodic table about which there is no consensus. The periodic table should be shown in a short-form as this is the form in general use in text-books, wall charts etc. It would be preferable if the names of the elements are shown in their respective boxes as the blank boxes are uninformative. The short-form illustrated at http://iupac.org/publications/ci/2004/2601/2_holden.html is a good candidate for use in chembox/infobox. Petergans (talk) 10:55, 6 December 2013 (UTC)
What elements? When I look at Hydrogen and Astatine, they both use {{elementbox}}. The sidebar box themselves are in a separate templatespace page instead of being directly coded in the article. That seems to have happened in 2008/2009, when they used the partial "elementbox_header"...etc construction templates system; sometime in 2010 it was converted over to the newer "elementbox" unified templates system. If you wish to edit the contents sidebar box, you click on the "E" at the bottom of the box. Check {{elementbox}} for the supported parameters. -- 65.94.78.9 (talk) 10:20, 7 December 2013 (UTC)
If you look at the source code for Hydrogen you will see {{Infobox hydrogen}} which apparently calls both the periodic table and the element box. The "E" applies only to the element box. Petergans (talk) 19:36, 7 December 2013 (UTC)
Well, you can easily create a long-form table from the short-form table, so what's the problem? The long-form fits better in the space provided. And since we have to choose in the long form between Sc/Y/La/Ac and Sc/Y/Lu/Lr, it's a pretty easy choice for the latter (as argued at length above); and they can be easily distinguished anyway. With the short-form, it's not immediately obvious whether Sc/Y/La/Ac or Sc/Y/Lu/Lr has been chosen, as there are no symbols: your PT image shown above shows the gap to the left of the d-block, while having the asterisked footnote after La (which is there in group 3), which would lead me to interpret that it was Lu under Y based on the position of the gap if there were no symbols! Double sharp (talk) 03:23, 8 December 2013 (UTC)
I understand you meant to write {{infobox element}} instead of {{infobox}} (or else please explain). BTW, the templates {{elementbox}} and {{infobox element}} are exactly the same (because of a redirect).
"Why, when and by whom ..." -- Only the "why" seems relevant. 'When' and 'by whom' can be found in the page history, and I don't read a question from there.
"agreed policy" - well, this is not a policy of course, but you can assume there is agreement. This is how we work at WP. From there, you can propose changes, preferably at WT:ELEM.
"Why" changed is that elements are a more specific subgroup of chemistry. The {{infobox element}} provides element-specific options, including the element's position in the periodic table. If you want options that are in {{chembox}} but not in {{infobox element}}}, please name them.
"How to edit" - simply by the v-t-e options that are below in the infobox. You can edit the element's content there. This is a common option in more templates at WP.
If you want to edit all element infoboxes, systematically, that is backgrund (meta) template editing. If there is a change proposed & agreed, there are editors (like me) who can implement the outcome. Nowadays no major changes can be "proposed" by editing the meta-template; simply go talkpage first. So far, this is about procedure and process, not about content. As far as I understand, it does not lead to a change.
"long-form" periodic table: if you propose to use an 18-column PT instead of a 32-column, that is a different topic in here (namely, not about template organizing). I can note that only some weeks exactly this was discussed extensively, now in WT:ELEM/Archive 16.
Thank you, user:DePiep for this clarification. I don't want to go over all the arguments again. Suffice it to say that I have the strongest objection to placing the main-group elements Sc and Y in the same column as the lanthanide Lu. The basis of our standard periodic table is electronic structure. That's why d-block and f-block elements are shown as separate blocks. I propose to show the the standard (18 column) periodic table at right rather than the long form in the info box. The 18 column form is uncontroversial. It requires less space, horizontally, than the long form. Indeed there is enough space for the element names to be included and be legible in their respective boxes, which would be much clearer and would remove the need for side-bars with before/after and above/below. The 18-column form is what students see in their text-books and wall-charts. In this context that is important. Petergans (talk) 14:59, 8 December 2013 (UTC)
Yes. Obviously fill in the missing transuranics: Fm, Md, No and then beyond Lr. Maybe add the element symbols in their respective boxes, especially if clicking the image would show the PT full-screen. Petergans (talk) 17:04, 8 December 2013 (UTC)
Some short remarks then. Yes, these heavier elements are there, they are colored white/lightgrey for being "predicted". No issue there. Then, you say "d-block and f-block elements are shown as separate blocks". But Lu, Lr are d-block (right?;No they are lanthanide and actinide elements respectively hence my question), while shown below with the f-block. Hmm. So these two blocks of course are there, but not actually shown I'd say -- actually they are cut. About the wording "are shown". That says the image aims (wants) to point them out. But that is a bit sloppy, because we do not aim to show any s- and p-block. This is confusing by being incomplete (again, they are all there we know, but not shown in the same way). In this I'd advise: let the table shows them by itself, without us having to stress anything.
Another argument you mention is "uncontroversial". I beg to differ: the verdict on group 3 is not definitive I think this refers to the 36-column table. In 18-column tables Lu is usually at the end of the lanthanide series and Lr at the end of the actinides. (e.g., as you mention Lr, and I ask what about Lu), and the reason for forking out the ~f-block may be from historical habit mostly (book printing + as-I-learned-it).Quite so, but it's important for precisely that reason The word "standard" we use may not be accurate any more. The argument "space" I want to get rid of right away, because in this infobox situation space is not an issue (it was in book printing, it is in other PTs here at WP). And overall, "standard" PT does not point to a single PT version; both facts & presentation differ seriously between available 18-column tables.No they don't. The only difference that I can see is whether La and Ac are written explicitly in group 3 or not. This is not a significant difference.
I think a 32-column PT can show all you want,Not so. I would like to see the element symbols rather than blank boxes. This is impossible with 32 colums and does not have the awkward mental issue of the displacement. D- and f-block even show automatically from the structure. in the steps. We don't have to add anything (we could color the blocks, all, when needed). Even with 32 cols we must work things out, but at least the cut & paste is prevented and can not introduce issues.
These are my points, rather quick just to mention them. Don't wanna start the debates here, because not central. The archived 18/32-col debate I already linked to. I can add that the topics of block 3 (Sc/Y/Lu/Lr?) and how to detail the 18-column PT are currently discussed at WT:ELEMENTS. I guess you might want to follow the discussion & joint the debate there. -DePiep (talk) 18:21, 8 December 2013 (UTC)
(Clashed with the comment below) My comments are in blue above. I am trying to avoid controversy as far as possible. The 18-column table is not controversial. Plus, the boxes that are blank at present make a very bad first impression. The 36-column table game is a minority sport best played on the field of the periodic table article. Petergans (talk) 21:03, 8 December 2013 (UTC)
So I only just discovered that a Group 3 discussion has happened on this page too. How confusing. I hope you can add to the central talk if you have any issue left. I prefer having you on board before whatever outcome. -DePiep (talk) 20:12, 8 December 2013 (UTC)
@Petergans: How are Lu and Lr not d-block elements? Sure they are lanthanides also.
No, Lu and Lr are not always placed at the end of the lanthanide and actinide series. Again, the placement where Lu and Lr are directly below Y is gaining quite a lot of ground.
Yes, there are major differences between the 18-column formats. You appear to think that the Sc/Y/*/** placement means La and Ac are below Sc and Y. No it doesn't: it means all the lanthanides and actinides are below Sc and Y. Just because * means La and following elements doesn't privilege La over Lu, Gd, Nd, Ho, or any other lanthanide. And Sc/Y/Lu/Lr is of course a different format. I suspect many of the texts supposedly using Sc/Y/La/Ac are really using Sc/Y/*/** and are therefore being wrongly counted here as being in favour of Sc/Y/La/Ac.
And again, the 18-column table translates immediately to the 32-column table; just put the lanthanides and actinides back in the asterisks' position. Many authorities speak of the 32-column table as better, and the only reason why you don't see it more often in print sources is because its aspect ratio is unforgiving for standard paper sizes. Double sharp (talk) 05:47, 9 December 2013 (UTC)
Re Petergans. Q: "are Lu, Lr in the d-block?" A: "No, they are lanthanide resp. actinide". ??? "Lanthanides" is a category, "d-block" is a block. Elements are in both. Two independent classifications. (There are more, like group).
About singling out the f-block. There is no reason to single out f-block, while not noting s-, p-, d-blocks. Aiming to do so is confusing, because is shows the blocks half-heartedly or quarter-heartedly. Compare: when ever was the d-block singled out to make some point? Only when you want to describe the d-block. Never in any standard PT.
DePiep: "the verdict on group 3 is not definitive" -- Pgans: "I think this refers to the 36-column [32-column?]". Whatever the issue in a 32-columns, it is not solved in an 18-columns. Obfuscated maybe in the 18-column. Scerri (2012) points it out.
Pgans, about visually singling out f-block: "Quite so, but it's important for precisely that reason".
"La and Ac are written explicitly in group 3 or not. This is not a significant difference". Constitution of group 3 is significant. It's just that in 18-columns, one can hide (ambiguously) this question. Also, you (not me) are mistaken in the block-suggestion.
About 32 columns, Pgans: "I would like to see the element symbols rather than blank boxes" ??? There are no elements there. Exactly that is what the peridic table shows. Great. Whether we like it or not. But I think you misread my point. I meant to say: Whatever you want to show in a PT, you can show it in a 32-column. There is not a single improvement by going to an 18-column. And personal preference does not count much I can add.
DePiep: 18-col is from "historical habit mostly" -Pgans: "Quite so, but it's important for precisely that reason". Habit is a low weight argument. Especially since this one is inherited from ~1945 and from book printing limitations. Also it introduced variants and misunderstandings/errors (as you demonstrate here: d-/f-block, group 3-membership). -DePiep (talk) 07:28, 9 December 2013 (UTC)
I understand the point that the 18-column table is “old-fashioned”. I think that the importance of familiarity to today’s students has been underestimated in the quest for something more “modern”.
There are equally good arguments for both the 32-column table shown now in the infobox and for what I have suggested above. In that sense the 32-column table will always be controversial.
Here’s my suggestion. Rather than continuing this discussion in the abstract why don’t you (DePiep) prepare an 18-column table, including element symbols, on the lines of File:Periodic Table overview (standard).svg The question of which to use can then be put to the wider WP community, showing both tables with the size as determined by the info box. Until then, I will not post any further comments on this topic. Petergans (talk) 09:32, 9 December 2013 (UTC)
It was moved to WP space, I've now moved it to article space but cross-space redirects from WP space remain. The AfC page now points to the article-space target. EdChem (talk) 12:36, 9 December 2013 (UTC)
Making the topic a little clearer to understand for learners
Latest comment: 10 years ago2 comments2 people in discussion
We learn just how important and powerful covalent bonds are in our world; so the next step is to explore them. With some simple pictures and real world connections, so many students can easily grasp covalent bonds and be interested to go deeper. So if I got my kids ready to go deeper, I need to be ready to go deeper. I followed to sigma bonding - the strongest type of covalent bond. Sounds pretty important. So, if it is so strong, why is this page so shallow and deep at the same time? I suggest someone who knows what they are talking about, and I am sure there are MANY, to teach in progression and maybe from different angles.
This page jumps to mention "σ orbitals have no nodal planes at which the wavefunction is zero." Definitions or links for "nodal plane" and "the wave function" should be addressed. Unless you're a mathematician and a scientist, you may have gotten lost here. if not there then maybe sooner at: "s+s, pz+pz, s+pz and dz2+dz2 (where z is defined as the axis of the bond).[2] " This reference in from 2002!! What is interesting to me here is that they are bonding on different axes, including the z, but can someone take it from here and explain it deeper or link more pages so I and other inquiring minds can take sigma bonding to the next level?! I got stuck when we talk about all the bonding of elements, but suddenly we are talking about s+s and such - what do the s's represent here? Inquiring minds need knowledgeable ones! Please add to this page, thank you! — Preceding unsigned comment added by 71.83.54.194 (talk) 05:46, 15 December 2013 (UTC)
Latest comment: 10 years ago1 comment1 person in discussion
Can someone add documentation to all these templates? The usage is not documented, (when and where these should be used, what the template is,, how to use the optional parameters, etc)
Latest comment: 10 years ago1 comment1 person in discussion
Mergers can be controversial, so I want to give people a chance before I do anything. An intermittent plan to merge these two articles has been underway for one year. The idea is that is that solvanted electrons, when crystallized, are called electrides. So for the sake of a coherent explanation for readers, the merger would seem to make sense. The discussion is here and here. Advice welcome, otherwise we do this.--Smokefoot (talk) 16:03, 22 December 2013 (UTC)
Temperatures in Chembox
Latest comment: 10 years ago3 comments2 people in discussion
Such a loss of precision is most undesirable. I would hope that the "round to" parameter could be used overcome this, but it cannot be if the template is used generically in the chembox. The question of precision (number of significant figures) arises with some scale changes, such as in this example. Petergans (talk) 15:22, 27 December 2013 (UTC)
Latest comment: 10 years ago2 comments2 people in discussion
Hi. I could use some help with the current FA nomination of the article on Josiah Willard Gibbs. Please take a look and comment as you see fit. Also, some time ago I mentioned here that I think Gibbs should be re-assessed as of Top importance in both chemistry (he's the father of physical chemistry) and physics (he's one of the three founders of statistical mechanics), and of high importance in math (he created vector calculus). I got no response back then, but I see no harm in bringing this up again. - Eb.hoop (talk) 20:08, 28 December 2013 (UTC)
This question is directed to the chemist. Anatabine is found in plants, when it is extracted for use in Anatabloc is it a full spectrum anatabine with all isomers or another state? I know little of chemistry so I hope my question is understandable.
Latest comment: 10 years ago10 comments3 people in discussion
We might move Phosphoric acids and phosphates to Phosphoric acids. Reason: we have phosphate and sodium phosphates, in addition to the usual articles on individual compounds. if no objections are registered, perhaps an administrator can help. Another reason: "Phosphoric acids and phosphates" is a huge area. My proposed plans are to shift most phosphate content to phosphate and add {{main| phosphate}} and {{main|sodium phosphates}}. In general, editors are invited to review articles in the Category:Phosphates and make suggestions here or on theie talk pages regarding content. Judging by the hit rate (http://stats.grok.se/en/201312/sodium%20phosphates), some these articles are visited hundreds of times daily. --Smokefoot (talk) 16:33, 5 January 2014 (UTC)
I consider that phosphoric acids and phosphates are inter-related, and the original article was written that way. Each type of phosphoric acid has a corresponding type of fully neutralized (deprotonated) phosphate. Furthermore, each type of phosphoric acid has multiple sites of acidity (protons that can dissociate), and there are multiple intermediate ions going from a fully protonated phosphoric acid to its fully neutralized specie, the phosphate. Accordingly, there are multiple Ka and pKa values for each type of phosphoric acid, and likewise multiple Kb and pKb values for each corresponding phosphate when going in the opposite direction (i.e. protonating corresponding base sites). It was a significant purpose of the article to point out the intermediate species and the interconversions. Of course, there is a separate single-compound Phosphoric acid article covering the very common mono- or orthophosphoric acid, for which a single compound Chembox is included. More or less analogously, the Phosphate article covers the mono- or orthophosphate, with little mention of polyphosphates for which there is a separate article covering the anions and esters. H Padleckas (talk) 04:08, 9 January 2014 (UTC)
Mea culpa, mea culpa - I should never have started this initiative. I will re-merge phosphoric acids and their conjugate bases and undo my damage. Later, I dont have time now. --Smokefoot (talk) 14:45, 9 January 2014 (UTC)
I will reproduce Dirk Beetstra's comments on this matter from his Talk page here:
I've answered [on the WP talk: Chemistry page] - basically I think that there should be an article describing the concept of 'polyacids', and separate articles (certainly for the phosphoric acid based ones) describing the different anions. The concept is there for many (sulfuric acid, carbonic acid, citric acid, maleic acid, malic acid), so an article on the concept is appropriate, and for some of the acids the anions are 'notable enough' to warrant all their own articles (certainly true for phosphoric and sulfuric, and probably for citric - all are 'sold' in mono-, di-, and sometimes tri-basic salts). --Dirk BeetstraTC04:25, 9 January 2014 (UTC)
I will respond to this comment and Dirk Beetstra's other comments above in this section simultaneously below:
In view of Dirk Beetstra's comments, I feel that the word polyacids is somewhat ambiguous. It could be taken to mean polyprotic acids whose molecules have more than one acidic site, typically where a proton could dissociate. Polyacids could also be taken to mean dimerized, trimerized, etc. (oligomerized, polymerized or polycondensed) smaller acid molecules or their neutralized anions such as polyphosphoric acids from mono- or orthophosphoric acid.
On March 21, 2005, I added a discussion on mono- and polyprotic acids to the "Chemical characteristics" section of the Acid article. Since then these have been changed to subsections in th Acid article called "Monoprotic acids" and "Polyprotic acids", to which some equations for fractional concentrations have been added. I'm thinking some mention of a tetraprotic acid with an example could be mentioned, and a mention of polyprotic acids with more than 4 acid sites could be mentioned, mentioning polypeptides/proteins and nucleic acids as examples. Also, the Acid dissociation constant article has sections on "Monoprotic acids" and "Polyprotic acids". This way, a discussion of "polyacids" with multiple acidic sites in a molecule would be covered. Also,
Considering the other possible meaning I mentioned for "polyacids", the multiple condensation or joining of smaller acid molecules, it is an established fact that orthophosphoric acid and orthophosphate can dimerize, trimerize, etc. this way, so an article describing this series of compounds is satisfactory. Other possible examples mentioned by Dirk B. include sulfuric acids and sulfates, carbonic acids and carbonates, and citric acid and citrate. Of these 3 types, the only such joined or polymerized acid(s) I have heard of are (is) disulfuric acid (pyrosulfuric acid) for which there is a short article. The corresponding anion is pyrosulfate (disulfate) for which there is a very short article, but there are articles on a couple of pyrosulfate salts. The Disulfuric acid article states "There are other related acids with the general formula H2O·(SO3)x though none are isolable." The Carbonic acid article essentialy states that this compound is unstable and easily decomposes into carbon dioxide and water, and that carbonic acid cannot be isolated except under very unusual circumstances. There is an article on Orthocarbonic acid, the hydrate of carbonic acid, but it is even more unstable. Thus it can be expected that di-, tri-, and multi-carbonic acids would also be unstable to the point they're hardly worth writing about. Carbonates and bicarbonates are stable. The Dicarbonate and Tricarbonate articles are about esters of such hypothetical di- and tricarbonic acids (implying they do not exist), but the Dicarbonate article states that the anion is apparently unstable but may have a fleeting existence in carbonate solutions. A similar tricarbonate anion is not mentioned. Polycarbonates are polymers with divalent organic groups between each of the carbonate moieties (-O-CO-O-) and are not really the kind of directly condensed carbonates we are pondering here. Such condensed polycitric acids and poly-other acids may exist, but I'm not sure they're notable enough to discuss in Wikipedia. So far, it seems to me that polyphosphates are either fairly unique or among the few types of fairly simple acids that can polymerize in the ways described in Phosphoric acids and phosphates. Therefore, I wrote this separate article on this series of compounds.
Another item to ponder: For all acids (or classes of acids), shall we write a corresponding article on the anion or specie resulting from neutralization, the conjugate base ? I would say it depends on the notability of the neutralized specie. If it is notable enough to write something worthwhile about beyond a paragraph or so, perhaps it deserves its own separate article. Otherwise, just mention the neutralized anion/ester in the [specific acid] article and the few tidbits of information there may be to say. H Padleckas (talk) 00:51, 11 January 2014 (UTC)
I knew something was wrong with my wording, I should have read what IUPAC says about it.
I meant the monoprotic/diprotic/triprotic/#-protic naming, and that that could be explained better separately. Though I also agree on having the polyacid (pyrosulfuric, pyrophosphoric, etc.). I think that Henry has been quite thorough in defining which 'common' examples there are (I also was thinking of the inorganic oxides, some of those also form acids: molybdic acid (diprotic), and some of that stuff has also the tendency to 'dimerize' forming polyacids). I think both concepts warrant a general article, more abstract and all the examples (where notable) should be hooked into those.
Now, for phosphates and phosphoric acid .. It is mainly the phosphate that is the special stuff in living organisms. It is known for its different acidities of the different protons, and for hooking up together (ADP, ATP ..). Not sure though if the free acids should be there as well (I don't think we have a notable amount of H3PO4 running around our bodies). Because of the ADP/ATP and all other phosphates in biology, maybe that should all be at Phosphates (biochemistry)??
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Localised bonding. Easiest to understand for beginners.
Localised bonding, but indication of stereochemistry.
Localised bonding, but delocalisation indicated by resonance structures.
Indication of delocalisation and stereochemistry.
Space-filling model, shows 3D shape without distraction of bonding detail - but sometimes hard to see all atoms.
Ball-and-stick model, showing full 3D structure and dashed bonds indicating delocalisation and equal P-O bond lengths.
Full 3D model of the crystal structure - lots of information but complicated at a glance. Tells you lots about the whole but less about the components.
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