Talk:Binary compounds of hydrogen

Table of dubious hydrides

In the periodic table there are a row of transition elements labelled as ionic. These hydrides are actually the interstitial metallic like materials, and so are not really ionic or covalent in the normal form. Also FeH₃ is hardly ever found and is the most extremely unstable molecule. It is unstable in the presence of others of its kind, and so it has to be kept separate in a solid noble gas matrix, so I do not think it is a good example to list. FeH, a covalent molecule, is observed in nature in "cool" stars. Graeme Bartlett (talk) 11:20, 26 December 2012 (UTC)

Actually, no, those particular hydrides are discrete molecules and not alloys. The table is not a list of examples, it is a table of the highest subhypervalent hydrides. Plasmic Physics (talk) 20:26, 26 December 2012 (UTC)

Well if you are interested in documenting the highest valence, then they are covalently bonded, and not ionic in nature, so the background colour should change for that first transition row, perhaps to intermediate if you have evidence of the bond nature. Also what are "Non-classical molecular hydrides"? We need an explanation in the text. Only triatomic hydrogen is linked, and that is extremely unstable, not even surviving by itself! Graeme Bartlett (talk) 22:08, 26 December 2012 (UTC)

All bonds have some ionic character; the distinction is made by the major contribution. Plasmic Physics (talk) 02:07, 27 December 2012 (UTC)

Yes, can you explain the Non-classical molecular hydrides? V8rik (talk) 22:19, 26 December 2012 (UTC)

In Transition metal hydride, under Bonding motifs, there is a link to Dihydrogen complex. Plasmic Physics (talk) 02:07, 27 December 2012 (UTC)

• I did some research on the topic and my sources (ref 1 to 4 in current article) told me the elements in the "do not exist" box do not form hydrides. I did not take into consideration outer space. You can change the classifications of course but do so with proper citations. By the way, The chromium hydride article does not make it clear if you can actually buy CrH in a bottle from a shop V8rik (talk) 22:14, 26 December 2012 (UTC)

Indeed, but they are not subhypervalent. I don't know what you are implying with the chromium remark. Plasmic Physics (talk) 02:07, 27 December 2012 (UTC)

• • the article is unclear to me, I am interested to know how stable chromium hydride is. V8rik (talk) 21:14, 27 December 2012 (UTC)
    • Chromium hydride as a solid interstitial hydride decomposes slowly at room temperature, and rapidly when hot. The CrH gas molecule is stable in cool stars but will decompose when cooled to Cr liquid and H₂ gas, or it will break apart when heated enough. Graeme Bartlett (talk) 21:47, 27 December 2012 (UTC)

Periodic tables of binary halides

I see a number of fundamental issues with this article I shall briefly enumerate the ones that stick out in these two tables.

• This title is inappropriate. OH₂ is a definite chemical compound, MoH₆ is not. The only binary compounds included are AH_n no binary A_mH_n. This is a major omission from the article.
• Classical molecular hydrides
  • It is not clear whether we are looking at a molecular state, or the "normal state" of the compound. If the latter why say "classical molecular hydrides" when some of the compounds are not molecular. And what does classical mean in this context?
  • The classification system, covalent, ionic, intermediate is unreferenced
  • Intermediate hydride, intermediate between what? If it means covalent/ionic which is implied by the ionic and covalent categories then that applies to some but not all of the "compounds" mentioned. If intermediate means ionic /covalent aren't many of such bonds usually classified as polar covalent. Note electronegativity dofferences between and H and the vast majority of other elements means that nearly all covalent bonds to H are polar.
  • The classifications of individual compounds are unsupported by references. Some look wrong, for instance InH₃.
  • The d block, lanthanide, actinide hydrides what are being referred to here? Are these molecuar forms or are these the non-stoichiometric phases and if the latter why have some been chosen in preference to others? e.g. ScH₃ is in the list rather than ScH₂
  • If this refers to the solids what does the term intermediate mean here, can't be covalent/ionic can it- many of these have metallic conductivity.
• Non classical molecular hydrides- unreferenced term non-classical, these are dihydrogen complexes, why not simply call them that?
  • Not one single reference to back up the existence of any of these complexes

Axiosaurus (talk) 08:42, 19 September 2013 (UTC)

MoH
₆ is most definitely a stoichiometric compound. Do you have a reference that says otherwise? I have answered a few questions by expanding the description within the section. What do you mean by, "some look wrong"? What looks wrong about indium trihydride? Plasmic Physics (talk) 12:27, 19 September 2013 (UTC)

Being helpful see Wiberg for MoH₆. InH₃ is polymeric, it therefore contains hydrogen bridges, It is therefore similar to solid gallium hydride which is called covalent, and for GaH₃ that seems a reasonable description. If you have a reference for InH₃ classification and all the other compounds, you should put them in the article. The content of the article has to be decided upon and expressed clearly in English. I am confused as to what the first table holds, is it molecular hydrides or solid state compounds or what? I do not see a definition of the classification or references to it, I do not see references for all of the "compounds" which have been classified. These are the big issues, the apparent mistakes are just the tip of the iceberg. Axiosaurus (talk) 12:59, 19 September 2013 (UTC)

I don't have a access to printed secondary sources, including "Wiberg", if that is what it is. What I do have, is access to the most recent spectroscopic research articles, and they say that MoH
₆ is an unstable molecular compound, that autopolymerises into a network solid. 'Oligomeric' is distinct from a 'network solid' in this case. Solid gallium hydride contains distinct oligomeric molecules, whereas indium hydride does not. I have already amended the description to state explicitly that the compounds listed are molecular, however, the colour scheme applies to the standard state. I don't time for every single compound to be referenced right now. Plasmic Physics (talk) 13:23, 19 September 2013 (UTC)

I look forward to seeing the reference for MoH₆ , Wiberg is Holleman and Wiberg and it is available through google in "books" so you should be able to see the page. I note your inclusion of a definition of classical and intermediate which is welcome. I am still not clear on the definition of compound. You designate BH₃ to be covalent so presumably this refers to the gas phase monomer rather than the gas phase hydrogen bridged dimer, and the latter is what I would term the "standard state" form. More clarification required please. Just a point on the oligomeric form of gallane it may be oligomeric (needs a structure reference) but it is electron deficient, so intermediate to me would seem to be a better categorisation, I suggest you change the definition of intermediate. The categorisation of the transition metal hydrides concerns me, are these really all network polymers with bridging hydrogen? Once again references please. Hope you can find time soon. Axiosaurus (talk) 18:03, 19 September 2013 (UTC)

You ask for more clarification, however, it is unclear whether you refer to a preceding or succeeding concern. It would almost be easier to do away with ionic/intermediate/covalent altogether , so that it follows the second table's legend. Plasmic Physics (talk) 23:05, 19 September 2013 (UTC)

All of the above.+ what do you mean by standard state. Axiosaurus (talk) 09:03, 20 September 2013 (UTC)

A compound is by definition, a stoichiometric combination of two or more elements, which are chemically bound, and can only be separated by chemical processes. The best thing I can think of, is to wikilink it. 'Intermediate' has two requisites, electron deficiency, and a network solid standard state, as stated in the paragraph. How do you suggest I redefine it? If I reduce it to just electron deficiency, then the ionic classification would be lost, as they are also electron deficient. Plasmic Physics (talk) 23:23, 19 September 2013 (UTC)

NaH is electron deficient that is an unusual POV. Axiosaurus (talk) 09:03, 20 September 2013 (UTC)

I'll start with referencing as soon as the (Cite → Templates) editing tool becomes functional again. Plasmic Physics (talk) 23:31, 19 September 2013 (UTC)

• I can only give my view as to the way I have researched the topic based on references 1 to 4. See here for my last edit in this article, my sources explained to me Mo is inside the hydride gap. I am going to decline from commenting on edits by other editors V8rik (talk) 19:17, 19 September 2013 (UTC)

That is a problem, because there is no such thing as the 'hydride gap', it's more like the 'hydride knowledge gap'. Absence of evidence is not evidence of absence. It's not good scientific practice to call something impossible, just because you haven't observed it yet. Besides, that gap has already been filled for the most part. Plasmic Physics (talk) 23:13, 19 September 2013 (UTC)

FYI the hydride gap is described by Wiberg, and I paraphrase, as the elements Fe, Mo, W, Mn, Tc, Re, Ru, Os, Co, Rh, Ir, Pt, Ag, Au which do not form stable hydrides under normal conditions. Some of the compounds of these elements (e.g. FeH₂) you mention would not be considered by many to be stable hydrides under normal conditions. Not so much a knowledge gap but one of classification.Axiosaurus (talk) 09:03, 20 September 2013 (UTC)

I see. Plasmic Physics (talk) 12:19, 20 September 2013 (UTC)

I note that the classification scheme has changed- with a new category "standard state not assessed". Assuming I have understood the term correctly, I was surprised to see FeH₂ in this class as I understood it dissociated under normal conditions, and also surprised to see TiH₄ still classified as a network polymer as I understood that to be an unstable molecular form. So I will be interested to see the new evidence.Axiosaurus (talk) 09:03, 20 September 2013 (UTC)

I changed it to solid state. I corrected TiH
₄ to covalent, based on new evidence I found. Plasmic Physics (talk) 12:19, 20 September 2013 (UTC)

• Unexplained deleted content has been restored, the first part of the article now refers to stable hydrides is is well referenced by various general chemistry textbooks. The second part now refers to hydrides meeting other criteria. It would be worthwhile to have discussion first before deleting content. V8rik (talk) 17:47, 18 October 2013 (UTC)

What next?

We now have two tables- correctly in my view. Can I suggest that the "common items" classification is agreed upon and preferably be a referenceable standard from say Cotton and Wilkinson or some such source. Additionally the tables are contradictory for some compounds eg AlH3. Also a definition of stable would be helpful. Perhaps following this we could have 2 tables one for stable hydrides and the other for unstable, this would also allow the classification of the unstable t metal et al molecular hydrides to be expanded if necessary.Axiosaurus (talk) 14:34, 24 October 2013 (UTC)

• Table number three is still dubious and completely unreferenced, it lists FeH2(H2)3 but this compound is not mentioned in FeH2. If it continues to be unreferenced it should probably go. Any discussion on the unstable & esoteric & cryogenic hydrides is more than welcome, it is also possible to create a dedicated d-block table. AlCl was classified as covalent and stable after consulting refs 1 - 4. V8rik (talk) 20:15, 24 October 2013 (UTC)

I would agree with a separate d block table - perhaps we could put the decomp temperature in the box of the first table (just ones where decomp below room temperature). - I've seen that in some text book can't remember where. The third table is simply a list of H2 complexes detected in the laser ablation process. these are compounds, but it needs referencing. sorry untagged Axiosaurus (talk) 19:55, 27 October 2013 (UTC)

I see some rather odd edits from PP! Why is the stable hydride of zinc the solubility limit of H in Zn expressed as stoichiometry (presumably-- unreferenced so difficult to tell) bizarre.Axiosaurus (talk) 19:55, 27 October 2013 (UTC)

The zinc compound is already listed in the table below, there is no point in having duplicates. That is why I replaced it with the zinc-hydrogen alloy with maximum hydrogen content. Plasmic Physics (talk) 22:43, 27 October 2013 (UTC)

• work on the molecular hydrides is continuing by one editor but my earlier criticism (see above) has not been addressed, I tagged the page some time ago (https://en.wikipedia.org/w/index.php?title=Binary_compounds_of_hydrogen&oldid=577740397) but this tag has since been removed. If the existence of a compound like RuH2 or RuH2(H2)4 is presented as a fact on this page there should be a citation. That goes for every compound that is introduced here (not counting compound that already have a dedicated page). V8rik (talk) 17:05, 21 July 2014 (UTC)

Recent edits

I hope that the recent changes to the article are work in progress as there are a number of issues introduced. For example the new column which includes group 18 compounds with no explanation that some are excimers and the duplication of common well known hydrides into the table with different heats of formation from those quoted elsewhere in the article. Also what is "heuristic valence". Axiosaurus (talk) 10:56, 29 June 2014 (UTC)

I'll remove the excimers (He-Kr) I did not previously consider a non-zero activation energy as key requirement for an item to appear in the table. Yes, well-known hydrides are duplicated between the tables, however that is to allow for a fair comparison to be made with similar hydrides on the same playing field, as was the original purpose of the table. The heats of formation in the second table relate to the monomeric hydrides, not the standard state of those hydrides. The vaporal heats of formation are more useful to demonstrate the relative instability, and often have greater availability than the standard heats of formation. They also give a rough indication of a monohydride's tendency to undergo aggregation to a more energetically stable state. The heuristic valence is the valence which characterises the group, while strictly obeying the octet, dodectet, octadectet, hexadectet rules, etc. Plasmic Physics (talk) 12:20, 29 June 2014 (UTC)

Fine - it would be worth spelling out the details you've mentioned so as to clarify the article. Axiosaurus (talk) 15:21, 29 June 2014 (UTC)

Comments about how it is now, there is a lack of references. Some sentences are incomplete or misleading. Some substances mentioned are not binary compounds of hydrogen. There are some contradictions. The colour scheme used in the first two periodic tables does not match, this just makes things less clear. What assessed or not-assessed is unexplained on the page. Also there is a lack of units for the enthalpies.

For the recently changed intro to the molecular hydrides, there is an improvement, but still a lack of references. The monomeric hydrides have a wrong emphasis now on the most obscure and hard to make ones, whereas the common ones like methane, water and hydrogen chloride are not mentioned. Plasmic has not followed the requirement to include references. Though the material is not controversial, just seriously inbalanced. Graeme Bartlett (talk) 07:40, 6 December 2014 (UTC)

The main problem is the lack or references. The addition of the molecular metal hydrides albeit low temp, matrix isolated is informative. To be fair on Plasmic Physics, the embargo on editing has prevented him adding these refs. Hopefully he will be able to soon. Once these are in place I think a discussion on how to improve the format of the article would be appropriate.Axiosaurus (talk) 13:33, 6 December 2014 (UTC)

Well I think the consensus here is that PP should add the references. The molecular section is not wrong or useless, it just does not talk about the common hydrides. Graeme Bartlett (talk) 14:22, 6 December 2014 (UTC)

Hydrogen solutions

This new table is shaping up nicely. Just a question. My understanding was that Sieverts' law held for most metals, the p^1/2 indicating atomic H. There are cases where hydrogen interactions cause a deviation from Sieverts' but these are not, at least in lit. I have seen, indicative of H₂. the presence of molecular H₂ would be interesting.Axiosaurus (talk) 09:33, 13 January 2015 (UTC)

I miss the question. Are you confirming whether dihydrogen can act as a solute? Plasmic Physics (talk) 11:38, 20 January 2015 (UTC)

No, H₂ solute would be a new one for me. I thought that it was always atomic H in solution.Axiosaurus (talk) 13:42, 20 January 2015 (UTC)

I do believe that it is mainly a high pressure phenomenon. Plasmic Physics (talk) 20:20, 20 January 2015 (UTC)

Have you a reference?Axiosaurus (talk) 10:04, 21 January 2015 (UTC)

I'm afraid that I've lost it. However, I do remember the that paper mentioned an interesting fact about the investigated system: that it undergoes a certain change at a critical temperature. Apparently, above this temperature, the dihydrogen molecule undergoes free rotation within its interstitial site, effectively acting as a spherical entity, or a single atom (larger than the hydrogen atom). Below this temperature, this motion freezes out at once. It is definitely not something that I made up. Plasmic Physics (talk) 10:49, 21 January 2015 (UTC)

No problem. there are a lot of references in the lit. of solubility of molecular H₂ in silicon and germanium- so a slight change to the lead of the paragraph would do it.Axiosaurus (talk) 14:15, 23 January 2015 (UTC)

The new table is a bit wide, and part of the problem is the notes "nb 1" etc. The notes mentioning the graph are useless as there is no context to tell us what the graph is. If a foot note is needed, how about putting the link under the element symbol, so the boxes are a bit taller rather than so wide? And also where the foot note is the same, link to the same foot note, so we don't have so much repetition. Graeme Bartlett (talk) 21:25, 19 January 2015 (UTC)

How do you suggest I move the nb and ref below the formula within the cell? Will <br/> work? Plasmic Physics (talk) 11:38, 20 January 2015 (UTC)

Just use <br/>. Graeme Bartlett (talk) 12:06, 20 January 2015 (UTC)

Binary hidrogen anions

This article doesn`t cover binary hydrogen anions, such as [ReH₉]^- or [TcH₉]^2-. 𝕍𝕀𝕜𝕥𝕠𝕣 𝕐𝕒𝕟𝕖𝕧 (talk) 11:01, 27 November 2021 (UTC)

That would be because an anion alone is not a compound. And the compounds with them would be ternary compounds of hydrogen. I am looking for the generic term for these anions, is it hydridoanions? (in the same style as oxyanions?

I suppouse that this name is quite correct hence the nomenclature says nothing aginst it. 𝕍𝕀𝕜𝕥𝕠𝕣 𝕐𝕒𝕟𝕖𝕧 (talk) 14:43, 28 November 2021 (UTC)