Talk:Hydrogen/Archive 2

Archive 1

Archive 2

Archive 3

Disputed

Notice of the edit dispute mentioned above has been placed on the WikiProject Elements noticeboard. Since this is a Featured Article, ALL disputed content must be backed up by publications from well-recognized, reputable publishers whose editors fact check or (better yet) peer reviewed journals. Please fix the text to this standard ASAP; text that does not follow Wikipedia's standards of verifiability and relevance will be removed after review by WikiProject Elements members. The disputed tag needs to remain until there is consensus that the article follows Wikipedia content policies. --mav (talk) 02:19, 23 April 2008 (UTC)

Highest atomic weight per nucleon for all elements

I noticed that apparently H-1 (closely followed by the other H-isotopes) has the highest atomic weight per nucleon (1.00785 u) of all currently known isotopes (even more than the heaviest synthetical element, ununoctium, whose isotopes have values of about 1.0007 u per nucleon). Since nuclear reactions only happen naturally if the mass of the resulting particles is smaller than that of the original one(s) (mass=energy by Einstein), this means that hydrogen is in a certain way the "least stable"(!) of the 117 known elements. I don't know if this falls under OR, otherwise it would be a nice "trivia" to add to the article. --129.70.15.202 (talk) 20:33, 13 May 2008 (UTC)

It's the least energetically stable with respect to fusion processes, sure, but fusion is not generally thought of as a kind of radioactive decay. When we talk about "stablity" it's a given that radioactive decay (involving one nucleus to begin with) is all we're talking about. SBHarris 04:04, 13 July 2008 (UTC)

Hydrogen Safety Appears to Still be Steeped in Mythology

It would be good to see more data on the safety of hydrogen use, without the gratuitous picture of the Hindenburg in flames. The fact is; most passengers and crew on the Hindenburg survived the "disaster" and "walked" away from it.

The same volume of gasoline would have incinerated most of New Jersey! (comment required for parity in sensationalizing gasoline disasters)

````Dan Foster —Preceding unsigned comment added by 70.119.228.213 (talk) 02:42, 22 May 2008 (UTC)

Speaking of safety information, there seems to be an inconsistency in the autoignition temperature for dihydrogen, both within Wikipedia and beyond. On this page, it is reported as 560 degrees Celsius, correctly reproducing the value of the indicated reference. In Autoignition Temperature, the recorded number for dihydrogen is 536 degrees Celsius, again correctly reproducing the value indicated at the relevant reference. I have also seen 585 degrees Celsius here. Given the spread, perhaps it would be prudent to indicate that the autoignition temperature is between 500 and 600 degrees Celsius, or something to that effect. --Golfit (talk) 20:57, 4 September 2009 (UTC)

Energy carrier

The article flatly states that Hydrogen is not an energy source; which is both ambiguous and contradicts the document it references. Hydrogen CAN be an energy source even apart from nuclear methods. It can be used in place of petroleum. The only caveat is that it uses more energy to produce then it equivocates. But so what? This is a thermodynamic given. —Preceding unsigned comment added by Nathan.tuttle (talk • contribs) 01:03, 13 July 2008 (UTC)

It's not a given, as many people don't understand it. Hydrogen is an energy source in the same way a battery is. It's no help to world energy problems except as a storage reservoir. That's not so of sunlight, fossil fuels, or fissionable elements. Perhaps the section could be re-written so it cannot possibly be misunderstood. SBHarris 04:08, 13 July 2008 (UTC)

A New Fuel

Hydrogen as a powersource is looked down upon by wealthy oil industries but the pros really outweigh the cons. Hydrogen does not waste energy. Right now when there are too many amps being generated they have to shut them down however, with a hydrogen system the power can be stored in tanks without decay of energy. (unsigned)

Any system wastes energy making the storage form. You waste energy turning excess power into hydrogen, and you waste it when you pump water back uphill (as used to store excess generating capacity now). You could use the energy to make sythetic methanol out of water and CO2 from a powerplant, and store that (at room temp and pressure, with a lot fewer problems than hydrogen). That's what green plants do: they use solar to make hydrogen from water, but not being able to store it, they use it immediately to turn CO2 into more easily stored fuels-- glucose, starches, oils, etc. Humans can do the same-- it's just chemistry. See Hydrogen economy SBHarris 02:32, 13 August 2008 (UTC)

Laboratory Section -- making hydrogen from aluminium and bases

{{editsemiprotected}} The equation in the section on making hydrogen from aluminium and bases does not agree with the text, inasmuch as it represents a reaction with water, not base. I suggest changing it to the following:

2 Al + 6 H<sub>2</sub>O + 2 OH<sup>-</sup>→ 2 Al(OH)<sub>4</sub><sup>-</sup> + 3 H<sub>2</sub>

CharlesHBennett (talk) 02:09, 22 October 2008 (UTC)

Done--Aervanath lives in the Orphanage 04:52, 22 October 2008 (UTC)

Split proposal

I would like some input on a split, to keep this article about hydrogen as a chemical element with the symbol H, as it was as a FA-Class article, and move the rest of the information (the later extended sections on production, etc) to the page Gaseous hydrogen , or Dihydrogen H<sub>2</sub> , thanks Mion (talk) 12:42, 15 November 2008 (UTC)

That's a joke, right? As the two pages you mention do not exist, and redirect to this one. The production section is not that long. Methods of production of the free element are entirely appropriate to element articles. If the section on hydrogen got is getting too long, this simply would means that most of it should go to the

Main article: Hydrogen production

article (if there's something not already there), leaving a main-direct and a summary HERE. That's how WP grows. I've added the main article reference. And try not to waste our time, okay? SBHarris 18:14, 15 November 2008 (UTC)

The proposel stems from NL, they completed the split already, nl:Waterstof (element) and nl:Diwaterstof , a number of other wiki's do the same under dihydrogen , es:Dihidrógeno, fr:Dihydrogène, pl:Wodór cząsteczkowy and pt:Gás hidrogênio, so its no joke, but a serious proposal Mion (talk) 18:30, 15 November 2008 (UTC)

You're basically talking about splitting up this particular element article into an article on the free element, and another on its chemistry and its role as part of compounds which contain it. That's not unreasonable, but it's not been the way we handle things on en.wiki. Personally, I'd rather keep an overview article covering all of these things plus more (see the nitrogen article), and if you must have separate ones on the element itself (but see Hydrogen atom) and another on the compounds, as more info comes in, then spin them off as more detailed subarticles, and expand them (so we have three: hydrogen, hydrogen (free element) and hydrogen (chemistry). But this is a general question which you should take up with Wikipedia Talk:WikiProject Elements and user:Itub here on en., not on this specific page. SBHarris 20:38, 15 November 2008 (UTC)

Good idear, i'll put a note on the pages, as it was ment to open the discussion there is no hurry with it, Cheers Mion (talk) 21:15, 15 November 2008 (UTC)

I think the proposel is two pages Hydrogen and Dihydrogen, I dont see what would be left for a third page but maybe we should wait for the others to have a say, i left a notification on both pages. Cheers Mion (talk) 21:32, 15 November 2008 (UTC)

I have a little bit of problem, what the difference between hydrogen the element and dihydrogen might be. The atomic hydrogen has its own article and if necessary the articles like hydrogen production ... can get some info from the main article, but the production has a place in every element article. So can't see a split which gives us problems in the next FAR, because we miss a good deal of information.--Stone (talk) 22:29, 15 November 2008 (UTC)

I don't think that this article is particularly long. The only serious concern I see with the article is that a lot of the times hydrogen and dihydrogen are used interchangeably. I am a bit surprised that at the last FAR this was not solved. The only thing this article needs is for someone to go through each instance of use of the word "hydrogen" and rewrite it as either "dihydrogen", "hydrogen atom", or "the element hydrogen". Otherwise there could be a "Dyhydrogen molecule" article that discusses the bonding in more detail, without really needing to remove anything from this page. Nergaal (talk) 23:24, 15 November 2008 (UTC)

I suggest we lose the idea of an article on dihydrogen. Unless you want one on dioxygen. Another on trioxygen, and tetraoxygen, and 4 more for the various selenium allotropes, etc, etc. Put under enough pressure, and hydrogen (element) probably becomes a metal. Dihydrogen is just an allotrope (one we're familiar with) but it's not a synonym for the free element. And I think it sets a bad precident to think of it that way-- it's just what I call "STP bigotry" ;). SBHarris 23:54, 15 November 2008 (UTC)

Ok, i follow, rename every instance of hydrogen to dihydrogen and the matter is solved. Mion (talk) 00:13, 16 November 2008 (UTC)

It is NOT solved. Most hydrogen in the universe is monohydrogen. In fact, most of the normal matter mass of the universe is monohydrogen. Most of stars is hydrogen ions (plasma) with no "di". In the cores of planets like Jupiter, hydrogen is metalic, no "di." Dihydrogen is just the allotrope you're used to seeing, but it is NOT the free element. It's a very rare form of the free element. SBHarris 03:39, 16 November 2008 (UTC)

Articles on individual allotropes are perfectly fine when the allotrope is notable and there is enough to say about it. We have metallic hydrogen, ozone, tetraoxygen, graphite, diamond, and even the spin isomers of hydrogen. However, when there is an overwhelming "default" allotrope (as far as human chemists on Earth are concerned), then it is treated in the element's page as "the" free element. This mirrors the treatment given in every chemistry book I've seen. Calling H2 dihydrogen everywhere is just pedantry IMHO, akin to calling water dihydrogen monoxide. In some places it may be useful for emphasis or clarity, but when talking about uses and production of hydrogen, it is pointless until we actually start producing and using significant amounts of other allotropes.

I think there is definitely room for an article on the hydrogen molecule to parallel the article on the hydrogen atom and the helium atom; that is, an article on the theoretical treatment and significance of the hydrogen molecule. But I don't think that's what the original poster had in mind. --Itub (talk) 09:54, 16 November 2008 (UTC)

I looked at the wiki pages in Spanish, French, and Dutch, and if their goal is to really split the abstract element hydrogen from the elemental substance dihydrogen, they have done a poor job so far. Otherwise why do the infoboxes of the hydrogen article have melting points, densities, etc. all of which are for dihydrogen? The text of the articles is just as mixed. IMHO, because it is really hard to separate the two concepts without ending up with really awkward articles, which is why I prefer the approach taken by the English Wikipedia so far. -Itub (talk) 10:13, 16 November 2008 (UTC)

The interwiki pages are work in progres as wel, the discussion was started here to point at a problem in this former FA article, and looking at the comments, following Nergaal there is an easy solution to it, make a better distinction between the free element and the allotrope in the article and see how it turns out. Mion (talk) 10:37, 16 November 2008 (UTC)

What former FA article are you talking about? Last time I checked, this is still FA. --Itub (talk) 11:01, 16 November 2008 (UTC)

My mistake Mion (talk) 11:06, 16 November 2008 (UTC)

Per Summary Style, I think we should have (or eventually have) allotropes of hydrogen, hydrogen production, chemistry of hydrogen, isotopes of hydrogen, hydrogen safety, history of hydrogen, compounds of hydrogen, etc. Each of those will (or are) main articles that provide a more in-depth treatment of the summaries provided in sections here. I'm strongly opposed to the creation of dihydrogen or gaseous hydrogen b/c that would require the duplication of much of the content already here and likely result in three very confused articles. In short, leave hydrogen as the overview article and go into more detail on subtopics in daughter articles. --mav (talk) 14:46, 16 November 2008 (UTC)

Oh, and I don't see the length of any of this article's sections as an issue per WP:SS. In time, some sections will become larger than needed in this article. When that happens, that material should be summarized here and the detail moved to a daughter article. In fact, the overall length of this article (4600 words), may be a bit on the short side for such an important and expansive topic; articles are not normally considered "long" until they are in the 6000 to 10000 word range. Only long articles are normally split candidates with importance, scope and readability used to justify the extra reading time. --mav (talk) 15:10, 16 November 2008 (UTC)

Yes, WP:SS as sensibly invoked above by user:Mav is the standard Wikipedia procedure for growing material, and indeed should guide us here. Thanks for the reminder. SBHarris 02:09, 3 December 2008 (UTC)

Solid Hydrogen/Hydrogen merger

I'm suggesting that we merge the "Solid Hydrogen" article, which is nothing more then a stub into a new section on this article. I'm bringing it up here because there isn't a talk page there, and here is where someone with the necessary Wiki finesse to make it happen is going to see it.Pstanton 01:51, 3 December 2008 (UTC)

• Oppose merger. This page is already 67k long. We should be looking to split articles off from it, not include more material. Johnfos (talk) 01:58, 3 December 2008 (UTC)
• Oppose as for User:Johnfos, we need to increase the content of solid hydrogen instead, not reduce it to nothing. Graeme Bartlett (talk) 02:23, 3 December 2008 (UTC)
• Oppose As per discussion above and WP:SS. Mergers are hardly ever good unless you find two articles differently named, about the same thing. Otherwise mergers inhibit growth. Stub articles and WP:redlinks are how Wikipedia grows. SBHarris 02:00, 4 December 2008 (UTC)
• Oppose. But, please add link to "See also", so navigation between becomes easier. The same for other related articles.

--Vchorozopoulos (talk) 15:07, 16 December 2008 (UTC)

The merger proposel is closed, no support. Mion (talk) 09:39, 8 January 2009 (UTC)

spelling error

In the thermochemical production section, last sentence: "thermo_chemical methods" should be written together. Someone with access to this protected article, please correct it. Alexey Morgunov (talk) 12:42, 25 December 2008 (UTC)

Done, thanks for noticing Mion (talk) 13:05, 25 December 2008 (UTC)

Found just one more --> applications: energy carrier: first paragraph: last but one sentence: "hydrogen functionS". Alexey Morgunov (talk) 13:43, 25 December 2008 (UTC)

Done, I thought SBHarris checked the page ? -:) Mion (talk) 13:51, 25 December 2008 (UTC)

Yikes, I'm a terrible speller. Any saved versions I make only imply that I just killed some small vandalism or error of my own or somebody else's just made, not that it's a complete carefully-edited and vetted edition! SBHarris 02:09, 21 May 2009 (UTC)

Paracelsus

The reference 9 is supposed to mention Paracelsus but it doesn't. Andres (talk) 17:25, 1 March 2009 (UTC)

ref 59 . Mion (talk) 18:41, 1 March 2009 (UTC)

Word origin?

I was looking for the origin of the word hydrogen. Specifically, does it have anything to do with the Greek word for water, or does it originate somewhere else? Should this not be at the beginning of the article?

Daniel.dalegowski (talk) 16:23, 6 April 2009 (UTC)

It certainly does have to do with water. It means something like “creates water”, as oxygen means “creates acid”. In German it's called Wasserstoff, i.e. “water substance”, and oxygen is “Sauerstoff” = “acid substance”. Yes, I think the information should be in the article. We would need a reference, though. David Olivier (talk) 10:30, 8 April 2009 (UTC)

This information is already in the history section. --Itub (talk) 13:06, 9 April 2009 (UTC)

Element zero

Above the periodic table picture on the right, there is a caption stating that below hydrogen, there is no element (“(none) ← hydrogen → helium”). While the existence of isotope zero of element zero is debatable, isotope one — zero protons, one neutron — clearly exists. Shouldn't it be included? David Olivier (talk) 10:30, 8 April 2009 (UTC)

The neutron is not generally considered a chemical element. --Itub (talk) 13:06, 9 April 2009 (UTC)

Should also be in Category:Biology and pharmacology of chemical elements ?

Shouldn't Hydrogen also be in Category:Biology and pharmacology of chemical elements ? Eldin raigmore (talk) 18:10, 16 May 2009 (UTC)

Eldin: be WP:BOLD and add these category tags to elements found in biology yourself! It's not a controverial edit. SBHarris 02:03, 21 May 2009 (UTC)

Hydrogen as indirect greenhouse gas

According to this article], hydrogen is a indirect ghg-gas. This means that aldough it does not act as a greenhouse gas itself, it worsens the effect of greenhouse gases already floating around in the atmosphere. This extra global warming should be calculated into the national ghg emissions in order for a emissionless economy to work. This would allow hydrogen use to remain carbon neutral in the calculation (simplifies calculation).

add in article —Preceding unsigned comment added by 91.176.13.194 (talk) 11:42, 4 June 2009 (UTC)

ZE Power Plant

Please see [2] as it might be of interest to this or other related articles. 204.40.1.129 (talk) 17:01, 16 July 2009 (UTC)

Phase Diagaram

I noticed a link to a phase diagram was given. However, the pressure range of this diagram is at millions of bars. Does anyone have a phase diagram for a lower pressure region? —Preceding unsigned comment added by S243a (talk • contribs) 06:44, 12 August 2009 (UTC)

Suppliers

Would it be reasonable to add a suppliers sub-section under production section? And mention that Air Products and Chemicals Inc is the world's largest supplier of merchant hydrogen? Reference http://www.airproducts.com/Products/MerchantGases/HydrogenEnergy/Products/HydrogenSupply.htm --Robbin' Knowledge (talk) 15:36, 16 October 2009 (UTC)

A source which is more credible would be nice. What does USGS or other neutral sources quote?--Stone (talk) 15:39, 16 October 2009 (UTC)

This article from Gas World refers to Air Products as the 'leading global hydrogen provider': http://www.gasworld.com/news.php?a=4352 And this U.S Department of Energy Hydrogen Analysis Resource Center provides data in support of this claim. It does not give a list of Global Merchant Hydrogen suppliers, but it does have 'Merchant Hydrogen Production Capacity in the U.S. and Canada by Company/Location (.xls)'. --Robbin' Knowledge (talk) 20:04, 29 December 2009 (UTC)

plz see WP:NOTDIRECTORY. thnx. Mion (talk) 23:50, 29 December 2009 (UTC)

Hydrogen and dihydrogen mixture

Hydrogen and dihydrogen are radically (if I may say) different ; they occur naturally in different places, the human use is different, etc. On all accounts you have to admit that, be it to the scientist or to the layman, they are different substances.

The first two sentences concern the atom. Then the third sentence, without notice, concerns the dihydrogen. Then the fourth sentence, still without notice, concerns the monoatomic species. And so on. While I am aware of the above discussion, a proper scientific article should not be that untidy, featured or not featured.

I believe at least the introduction should clearly separate sentences pertaining to the atom, and sentences pertaining to the molecule. --Environnement2100 (talk) 19:05, 2 November 2009 (UTC)

I've tried to fix this by only talking about the atom in the first part of the first paragraph, and making clear when the change to H2 comes. See what you think. SBHarris 20:35, 2 November 2009 (UTC)

Corrections

I've corrected the introduction because:

1. Some organic compounds do not contain hydrogen e.g. tetracholoromethane, tetrafluoroethene, PTFE, etc.
2. The Schrodinger equation can be solved for ions of other elements e.g He<sup>+</sup>.

Ewen 08:54, 29 October 2006 (UTC)

In the Applications section, it is noted that Hydrogen is used in preference to any other gas because of its high Thermal Conductivity but I think it should refer to its high Specific Heat Capacity.

If we are in fact talking about Thermal Conductivity then we need to show the value in the List of thermal conductivities. --Graham Proud 10:24, 17 February 2007 (UTC)

Could someone please delete the false statement in "Natural occurrence" "Still, hydrogen is the third most abundant element on Earth." Hydrogen is not the third most abundant element on Earth, it is the fourth, and that's not counting the earth's core (see the article on "Earth"). However, the article that statement is taken from "" is an appropriate reference to use in the later section on "Hydrogen as an energy carrier". Use it as a reference along with the other one at the end of the section. -- There is a grammatical error which is continuous in the discussion and in the article. "an Hydrogen" is correct gramatically; "a Hydrogen" is incorrect. Could someone fix this please Thanks from Luke [13th of May 2007] 2:30PM (AEST)

"An" precedes vowel sounds, the "h" of hydrogen is not silent. Femto 12:16, 13 May 2007 (UTC)

According to A and an, it's "a" for a voiced H (as in hydrogen), unless you're Cockney British and prone to h-dropping. JeramieHicks (talk) 15:13, 9 May 2008 (UTC)

-- There is another error in the first paragraph. You have ". . .tastless, highly inflammable diatomic gas . . . ." It should be "highly flammable." Thanks, Benzuki2, 5/16/08 —Preceding unsigned comment added by Benzuki2 (talk • contribs) 16:48, 16 May 2008 (UTC)

Comment: "inflammable" is not an error for "flammable". "Flammable" is a neologism that was introduced to replace the word "inflammable" because people thought the "in-" prefix denoted "not". It didn't; think "inflame". False vacuum (talk) 20:05, 19 February 2010 (UTC)

Indeed, but most safety guides recommend using "flammable" to avoid confusion among non-native speakers. Materialscientist (talk) 04:55, 20 February 2010 (UTC)

-- There's another error in "Protons and Acids" -- H<sup>3+</sup> —Preceding unsigned comment added by 85.232.196.151 (talk) 07:05, 21 August 2009 (UTC)

Thank you. It was a typo in template. Materialscientist (talk) 07:47, 21 August 2009 (UTC)

Emission Spectra

I think that we should change the current picture for hydrogen's visible emission spectrum from this:

to this one:

which is an actual photograph of it. The two leftmost lines are actually ultraviolet as they have wavelengths less than 400 nm. Jkasd 10:46, 17 October 2009 (UTC)

The description of the top spectrum clearly explains how it was obtained. There is no information for the bottom one. This is a considerable argument for a featured article. Even if it is a genuine photo, its color and intensity is probably distorted by the poor UV response of that camera. Materialscientist (talk) 11:01, 17 October 2009 (UTC)

Would it make a difference if the person who uploaded the picture explained how they obtained it? Anyways, the reason I brought this up is because I am actually working on making better emission spectrum diagrams, see here. I sort of felt that my diagrams would be an approximation to the "ideal" photo, so I find it interesting that you actually prefer the diagram. —Jkasd 11:16, 17 October 2009 (UTC)

First, having such spectra would be great. You probably know this page. It might sound odd, but yes, I prefer a diagram - describing the experimental conditions would raise more questions, such as calibration and linearity of the x-scale and intensity, detector saturation (which broadens the lines and distorts color), gas purity, etc, etc. In this particular case (simple gases) spectra are well known, and what we need is just a "picture". BTW, the x-scale range (e.g. 380-750 nm) and linearity (linear vs. wavelength or energy) should be specified in the figure description file. Materialscientist (talk) 11:42, 17 October 2009 (UTC)

I was not aware of that page, so thanks. I think the main problem with the diagrams is depicting intensity, so I will keep experimenting with my image until I find something satisfactory. Once that is done I will describe exactly how I obtained it in the description, along with what source I used for the image. —Jkasd 22:46, 17 October 2009 (UTC)

<--Outdent The other problem is that the left two lines ARE technically in the UV, even if you can take a color photo of them and have them show up as "violet." We define UV rather artificially as anything shorter than 400 nm, but we do that for a reason, since sensitivity doesn't cut off perfectly sharply, high power UV shows up very deep into the spectrum, and people without lenses can see even farther into it. As for film showing UV as "violet", it does so with UV farther into the spectrum than your eye can see! That all shows up as "blue-violet" (it causes a blue haze in daylight color photos unless you use a UV filter). In summary, there are 4 classical visible-spectrum Balmer lines (I believe this is all Balmer himself described), and the first photo shows them. If you want one that shows 6 of the lines in what we now recognize as the Balmer spectrum (the one ending in n=2), it should probably go in the Balmer equation article. SBHarris 22:57, 17 October 2009 (UTC)

I already changed the image in that article, since I felt it was more illustrative of the Balmer series than the diagram. I asked here on the talk page first because it was a featured article and so the current picture probably had consensus for some reason which I am now aware of. —Jkasd 23:08, 17 October 2009 (UTC)

Please don't forget that most substances (including our body and eyes) have strong luminescence under UV light. A practical example - most people see N2 (337 nm) and He-Cd (325 nm) laser lights not because they are strong, but because of luminescence. I usually show this to students: take some clean peace of metal, and the laser is "invisible" on it (watch out for reflections though !) then grease it with your fingers (or soap) and it will shine UV-blue. Another point - in reality very few people thoroughly calibrate intensity response (especially in UV) and often publish uncorrected spectra - this is to say that intensity ratio is very approximate in line spectra. Materialscientist (talk) 00:16, 18 October 2009 (UTC)

According to our article visible light, the visible spectrum is 380 nm to 750 nm, but ultraviolet goes up to 400nm. Those two left lines would then be both in the visible and the ultraviolet range if I'm understanding this correctly. Would it be better to limit the visible spectrum arbitrarily to 400 nm in this sort of diagram? About the intensity, are you saying that any published data is only approximate, and there isn't any formula that will predict the intensity? —Jkasd 01:29, 18 October 2009 (UTC)

Eye sensitivity doesn't fall abruptly and depends on a person (so as color perception), thus I would mention the range in the figure file (too bad that many don't). 380 or 400 nm is optional, just keep consistent. You can find relative line intensities for low-pressure discharges, but they are usually treated as very approximate as they do depend on the gas pressure and purity, and even on mundane things like spectrometer resolution and sampling rate (in other words, it is possible to experimentally quantify those, for certain specified conditions, but very few bother to do so). Besides, intensities only matter when you plot them in an X-Y graph, they are arbitrary on the strip charts anyway. Materialscientist (talk) 02:09, 18 October 2009 (UTC)

Hydrogen Density

Which substance has the highest hydrogen atoms density (in mole per liter)? —Preceding unsigned comment added by 91.99.165.194 (talk) 19:14, 28 December 2009 (UTC)

At standard temps and pressures, probably high density polyethylene, which comes out at 134 grams/liter or so (of course, it's a solid). Liquid hydrocarbons usually have about 100 g and hydrogen liquid roughly 90 g. SBHarris 20:05, 4 January 2010 (UTC)

What about solid hydrogen? Guiness book of world records says it has density of 1.1 kg/lit @ 57kbar, although it seems absurdly high. —Preceding unsigned comment added by 91.99.166.80 (talk) 13:05, 26 January 2010 (UTC)

Added data to the infobox. Solid values vary between 0.076 and 0.088 g/cm<sup>3</sup>, I presume because of temperature (and maybe pressure). 0.076 is for melting point. Materialscientist (talk) 01:19, 27 January 2010 (UTC)

RELATED ISSUE

Under physical properties, density value given as(0 °C, 101.325 kPa) 89.88 g/L

This should read 89.88 g/m<sup>3</sup> or 0.08988 g/L , yes?? Cuzza (talk) 22:41, 9 February 2010 (UTC)

The latter; sorry, I've overlooked the recent change in the infobox but corrected it now. Materialscientist (talk) 23:24, 9 February 2010 (UTC)

Previous atom in the periodic table

Even though it is number one, I read in another wikipedia article about neutronium, made of only neutrons. If it is relevant even though it is only hypothetical, a link should be placed behind hydrogen.[[3]] --Arathun (talk) 14:21, 20 March 2010 (UTC)

where can i find hydrogen in. —Preceding unsigned comment added by 72.188.86.135 (talk) 13:44, 26 March 2010 (UTC)

All atoms should have mass in Kg

Why can't we say that the mass of hydrogen is 1.67372x10^-27 kg? —Preceding unsigned comment added by 139.140.112.101 (talk) 05:11, 5 May 2010 (UTC)

It's more convenient to give atomic masses and weights in universal atomic mass units (dalton = Da), where you don't have to deal with the exponent. You can always get the conversion from amu to kg in that article. SBHarris 05:50, 5 May 2010 (UTC)

splitting Hydrogen (atom) and Hydrogen (Element, H2)

Shouldn't we split hydrogen (H) from Dihydrogen (H2)? They aren't the same thing!! —Preceding unsigned comment added by Jipi d (talk • contribs) 15:51, 8 May 2010 (UTC)

opening

in the opening it says: 'In 1766–81, Henry Cavendish was the first to recognize that hydrogen gas was a discrete substance,[6] and that it produces water when burned, a property which later gave it its name, which in Greek means "water-former."' which does not seem like a accurate statement of the facts-- that Henry Cavendish was the first to recognize that hydrogen gas was a discrete substance does not seem accurate and is not sourced (for this recognition to have occured in the 18th century would seem strange), but also the statement 'and that it produces water when burned' is also inaccurate. Hydrogen is a part of water, and so cannot logically 'produce water' when burned. The preceeding statement about hydrogen being produced 'with acids and metals' is also inexplicable. So I'm going to remove all this from the opening. Any suggestions as to what it should be replaced with, if anything? (and we're all thinking about the same thing editing this page, right... hydrogen is the stuff that mixes with oxygen to make water... fluffy stuff clouds are made of (mostly)?) -sio. (talk) 17:53, 9 August 2010 (UTC)

"Burning" is a fancy word for "oxidizing"—that is, mixing with oxygen. H+O=water; thus, hydrogen produces water when it burns. – iridescent 18:08, 9 August 2010 (UTC)

If you think that the statement that hydrogen is produced by the reaction of acids with metals is "inexplicable", you probably know too little chemistry to be editing this article at all! Perhaps you could find another subject? SBHarris 18:31, 9 August 2010 (UTC)

Please clarify "Molecular Hydrogen" for dummies

I just read a NASA article talking about envisioning clouds of molecular-hydrogen gas. I feel sure this is simply (un-ionized) H2, so I wikipedia'd the term "molecular hydrogen", and was re-directed to Hydrogen. Ok, no big deal.

But nowhere on this page defines the term Molecular Hydrogen (although it appears several times).

Doesn't it seem proper for this term to be defined somewhere on wikipedia, and the Hydrogen page is a fine choice? Can I ask one of you, who know more physics than I and know this page, to define molecular hydrogen? Being an amateur, I want to make sure I'm not putting my foot in my mouth. Please help amateurs understand this simple(?) term. And delete this new Talk section of mine once you've done so.

Thanks! -RedKnight7 (talk) 03:05, 19 June 2010 (UTC) This might be in reference to hydrogen at the molecular level vs. hydrogen as it conventionally thought of as a super-abundant gas. Thats the only reason I can think of off-hand. -sio. (talk) 22:52, 4 August 2010 (UTC)

I completely agree because the physical properties section are a mix of hydrogen gas (H2) and the hydrogen element. The molecular weight is listed for hydrogen atom, where as everything else is for the gas. This article could be extremely confusing for some people. AGeorgas (talk) 18:15, 26 September 2010 (UTC)

Edit request from Jortx, 21 October 2010

{{edit semi-protected}}

Like the fifth link says the 75% of the Universe is not Hydrogen. The link says "Between 90% and 99% of the mass of the Universe seems to be completely unknown" and "Hydrogen composes about 75% of the mass of the Sun, ...", so this article is wrong about that.

Jortx (talk) 14:51, 21 October 2010 (UTC)

Not done. I'm assuming this is in reference to "...making up 75% of normal matter by mass...", (emphasis added) in which case, the operative words are normal matter which is linked to baryon. See also dark matter where it explains that "a small proportion of dark matter may be baryonic dark matter... however, the vast majority of the dark matter in the universe is believed to be nonbaryonic...". I think the sentence as written is correct, but if you have a suggestion for improved wording, please follow the instructions on the {{editsemiprotected}} template. -Atmoz (talk) 15:56, 21 October 2010 (UTC)

Yes. It's 75% of the baryonic mass, or chemical element mass, of the Sun (and the universe also). We know that most of the mass of the universe is dark energy and dark matter, which aren't chemical elements. We've made this qualification both in the lede (where it's qualified as "chemical element" matter, with a footnote) and later in the abundance section, where it's in a parenthetical remark. That's the best we can do. This article is not the place to have a full breakdown of the types of mass in the universe. I did some additional qualificatinal editing, and hopefully that's enough. SBHarris 01:10, 29 November 2010 (UTC)

Lifting Gas

Why is this semiprotected? Anyway, the Applications section needs to have a subsection about its use as a lifting gas. It should say that it provides 8% more lift than helium, and that it was used in gas balloons and airships but that its use has declined drastically since the Hindenburg disaster.63.3.9.1 (talk) 00:03, 31 October 2010 (UTC)

It's semiprotected because it was heavily vandalized. There are lots of references in the article to hydrogen being a lifting gas, but since this isn't a major use of it (actually, it isn't even a major use, in terms of %, for helium) it's more of historical importance-thing for hydrogen. SBHarris 00:57, 29 November 2010 (UTC)

Photographed

A hydrogen atom has now been successfully photographed. I think this is worthy of mentioning in the article, but do others agree? 203.45.33.202 (talk) 07:09, 28 November 2010 (UTC)

I suppose so. It's kind of a boring sphere, though. Not even cubical. I was hoping to see continents, weather, stain spots, or a mustache. Something. Perhaps we should wait. SBHarris 02:14, 29 November 2010 (UTC)

It is still worth mentioning. DO you have an exact wording that can be pasted in? Graeme Bartlett (talk) 07:43, 29 November 2010 (UTC)

Paracelsus & hydrogen

Although many sources claim that Paracelsus (1493-1541) was the first person to produce hydrogen and publish his observations, those sources are wrong. In a letter to the editor -- Leonard Dobbin (1932), Correspondence: "Paracelsus and the discovery of hydrogen," Journal of Chemical Education, vol. 9, no. 6, pages 1122-1124 -- Mr. Dobbin pointed out that the original source for this claim was wrong. Specifically, in neither the 1589 nor the 1570 editions of his book Archidoxa… does Paracelsus mention the production of gas from the reaction of acid with metal. Mr. Dobbin's claim was confirmed by Mary Weeks in her subsequent letter to the editor: Mary Elvira Weeks (1932), Correspondence: "Paracelsus and the discovery of hydrogen," Journal of Chemical Education, vol. 9, no. 7, page 1296. In her book Discovery of the Elements, Ms. Weeks repeated that Paracelsus did not produce hydrogen. See: Mary Elvira Weeks, Discovery of the Elements (Easton, Pennsylvania: Journal of Chemical Education, 1933), page 29.

The claim that Paracelsus discovered hydrogen seems to be yet another example of authors repeating what they'd read in an earlier publication without bothering to check the original source(s). Cwkmail (talk) 21:03, 29 November 2010 (UTC)

Edit request from Peterindelft, 20 December 2010

{{edit semi-protected}} Please change the reference to my page

Krogt, Peter van der (May 5, 2005). "Hydrogen". Elementymology & Elements Multidict. Retrieved 2008-02-20.

into the new url, which is

http://elements.vanderkrogt.net/element.php?sym=H The present link is dead.

Thanks,

Peter van der Krogt

Peterindelft (talk) 08:20, 20 December 2010 (UTC)

Done. Spacepotato (talk) 08:31, 20 December 2010 (UTC)

Thanks - I have now autoconfirmed status, so next time I can make the changes to these semi-protected pages myself. (Peterindelft talk) 09:59, 20 December 2010 (UTC)

Edit request from DNalepa Dec 20, 2010

In Applications section, please change: "...but the gas serves as a metallurgical problem as hydrogen solubility contributes in an unwanted way to embrittle many metals,..." to: "...but the gas's high solubility is a metallurgical problem, contributing to hydrogen embrittlement of many metals,..." I believe "serves as a metallurgical problem" is worse than awkward - serves what purpose ? a problem ? also in what WANTED way would hydrogen CONTRIBUTE to a problem? (serves/contributes means "add to") Thanks for reading69.40.254.72 (talk) 15:17, 20 December 2010 (UTC)

Done. SBHarris 01:56, 21 December 2010 (UTC)

Bad diagram radius

Depiction of a hydrogen atom showing the diameter as about twice the Bohr model radius (image not to scale).

I've been trying to get this redone for some time, but the original uploader seems to be a nonactive account, or is not answering requests. Twice the Bohr radius gives a diameter of about 1.06 = ~1.1 Å to two digits, not 2.4 Å. This diameter is wrong (too large) by a factor of at least two. Two times atomic radius is 1.6 Å, and 2 times covalent radius is 0.64 Å (it wouldn't be fair to use ionic radius). Diatomic hydrogen has a bond length of 0.74 Å, so even a molecule is less than 1.8 Å long (figuring inside 90% of electron density). So anything from 0.64 to 1.6 Å is fine (so long as identified), but 2.4 Å is just too big! I vote for 2x Bohr = 1.1 Å. Right now the diagram incorrectly says twice the Bohr radius is 2.4 Å SBHarris 02:13, 21 December 2010 (UTC)

Fixed :-D.

No, seriously, the charge radius of proton is either 0.84 or 0.877, it can't give "1.6 or 1.7".

2.4 is double of van der Waals radius, which is irrelevant here. The image is uninformative anyway, but it is used in many places, thus why not fix it. Materialscientist (talk) 03:51, 21 December 2010 (UTC)

Diameters are shown, not radii! Anyway, I'm talking about the radius of the atom, not the proton. For the proton, double .84 or double .877, results in 1.68 or 1.75. We could just leave it at 1.7 fm in diameter, and the loss of the third sig figure would take care of the proton measurement descrepancy problem. However, the radius of the electron cloud isn't nearly that close to being right, even to 1 sig figure. It's closer to 1 Å than 2 Å, by just about all measurements. ~ 1.1 Å, which happens to be twice the Bohr radius, would be a good compromise for the diameter. We have to show relative scale somehow. SBHarris 03:58, 21 December 2010 (UTC)

Please re-read my first sentence :-D Materialscientist (talk) 04:02, 21 December 2010 (UTC)

Oh, I saw it but paid no attention because it wasn't showing to me. Browser page-cache thing. Thanks! SBHarris 05:56, 21 December 2010 (UTC)

Edit request from Hermenwb, 30 December 2010

{{edit semi-protected}} The statement with which the "Energy carrier" section (http://en.wikipedia.org/wiki/Hydrogen#Energy_carrier) begins is not correct. Hydrogen is an energy resource. Liquid hydrogen is used in rocket propulsion (see http://en.wikipedia.org/wiki/Rocket_propellant#Current_Types) and there is nothing hypothetical about that.

Please change:

"Hydrogen is not an energy resource,[94] except in the hypothetical context of commercial nuclear fusion power plants using deuterium or tritium, a technology presently far from development."

to

"Hydrogen is used as an energy resource in rocket propulsion. However, for terrestrial applications, except in the hypothetical context of commercial nuclear fusion power plants using deuterium or tritium, hydrogen is not considered to be an energy resource [94]." Hermenwb (talk) 11:57, 30 December 2010 (UTC)

No, you're missing the point. Hydrogen is never used as a chemical energy resource, because it isn't found on Earth uncombined. When we use it in rockets, we might as well be using a battery. We have to use energy to make the hydrogen, then we get it back when the rocket fuel burns. SBHarris 20:39, 30 December 2010 (UTC)

Why

Why is there a star on the Afrikaans translation? —Preceding unsigned comment added by 66.108.76.50 (talk) 00:40, 14 January 2011 (UTC)

It means that it is of good quality. --Plasmic Physics (talk) 03:38, 14 January 2011 (UTC)

Error

I saw there's a link to tasteless, which has nothing to do with its real meaning. That link is just a guy with nickname tasteless.184.100.97.84 (talk) 00:51, 24 February 2011 (UTC)

Fixed. Thanks. Materialscientist (talk) 00:54, 24 February 2011 (UTC)

Enthalpy of combustion

Hi,

the enthalpy of combustion section is a little ambiguous. The reaction listed has two values, including one in brackets. Current text:

-- The enthalpy of combustion for hydrogen is −286 kJ/mol:[12]

   2 H2(g) + O2(g) → 2 H2O(l) + 572 kJ (286 kJ/mol)[note 1] 

--

The quoted figure of -286 kJ/mol is perfectly valid for 1 mole of H2 gas, but to illustrate that the reaction should show

  H2(g) + 1/2 O2(g) → H2O(l) + 286 kJ [note 1] 

Evan Robertson —Preceding unsigned comment added by 131.172.34.1 (talk) 23:37, 14 April 2011 (UTC)

Hi, I'm not sure how to use the discussion page on wiki, but I have a comment concerning the enthalpy of combustion for hydrogen : why is the output 2H20(l) ? Wouldn't the output be water in a gaseous form under most circumstances, giving an enthalpy of 199.9 kJ/g ? 192.75.139.249 (talk) 16:06, 1 June 2011 (UTC)

Tank pressure of liquid hydrogen at room temperature?

What is the pressure of a tank filled with liquid hydrogen at room temperature? (I am aware that it does not begin to liquefy until cooled to -260 C.)

Presumably, if the cryogenic liquid were put in a pressurized vessel just large enough to contain the liquid, and warmed to room temperature (about 20 C), it would not all be able to take the form of a gas and would have to stay mostly liquid just due to the confined space.

DMahalko (talk) 15:43, 5 May 2011 (UTC)

Cryogenic liquids stored at temperatures above their critical points are neither liquids nor gases, but supercritical fluids. They have no boundary interface, and don't "slosh" so you can think of them as an extremely dense gas. The pressure to store hydrogen gas at the same density as liquid hydrogen is what you'd get if you allowed a sealed tank of cryogenic liquid to warm up and become a supercritical fluid at room temp. It's enormous-- something like 13,000 psi or maybe 15,000. H2 compressed to 3,600 psi (about the pressure of a scuba cylinder) still has only 28% of the density of the liquid, so you can see how far you still have to go-- another factor of 3.5 at least, even assuming ideal gas behavior. Probably at least 4 times that. [4]. So if your tank won't take 15,000 psi or more and you do that trick, you're talking about a "bomb." SBHarris 17:28, 5 May 2011 (UTC)

Good to know, and probably worth being in the article. The next question is if there are any storage systems capable of 15,000 to 20,000 psi. Presumably the answer is yes, because water jet cutter technology uses pressures up to 100,000 psi.

The tank would likely have to be small to be workable, but still it would be interesting to know the costs of manufacturing say, a 1-inch diameter pressure vessel rated for 20,000 psi, and how it would compare in expense and energy capacity vs a mere 1000psi pressure vessel.

Also, note that any pressurized vessel might be considered a bomb, so although 15,000+ is very high, it is not necessarily any more hazardous than the components of a water jet cutter, if constructed properly.

DMahalko (talk) 21:07, 5 May 2011 (UTC)

The entire crew compartment of the Bathyscaphe Trieste endured 16,000 psi at the bottom of the Challenger Deep. A sphere is probably stronger in compression than tension (like an egg) but there exist 20,000 psi pressure vessels with very thick walls. They are very heavy-- several times heavier than the same volume of water. What's the point of such a thing? Have you read the article on hydrogen economy? There are more grams of hydrogen in a liter of gasoline or any alcohol (about 100 g/L), than there in a liter of liquid hydrogen (which has only 70 g per liter). Which is the same amount of hydrogen you get at these ridiculous pressures. If you just put your hydrogen in gasoline you can have the same amount with no pressure vessel weight. SBHarris 23:09, 5 May 2011 (UTC)

Hydrogen phase diagram

The old external reference Hydrogen phase diagram returns "access forbidden". I re-linked to High temperature hydrogen phase diagram Is this OK? Any better links? Jim1138 (talk) 08:46, 12 July 2011 (UTC)

Hydrgogen Filaments of Galaxies

About 1/2 of the missing matter of the universe is in the hydrogen filaments between galaxies. This is another credit to the abundance of hydrogen. See Summary "Astronomers find missing matter" — Preceding unsigned comment added by Matt.mawson (talk • contribs) 19:09, 15 September 2011 (UTC)

Phlogiston and inflammable air

{{Edit semi-protected}} "discrete substance, by identifying the gas from a metal-acid reaction as "phlogiston", meaning "flammable air""

should be replaced with:

"discrete substance, by naming the gas from a metal-acid reaction "flammable air". He speculated that "flammable air" was in fact identical to the hypothetical substance called "phlogiston""

Phlogiston doesn't mean inflammable air at all. It was a hypothetical substance introduced several years before to solve problems around combustion, smelting of metals, etc. Because the new gas he discovered matched some of the features expected of phlogiston (i.e. that it was light, that it could sustain combustion in ordinary air, etc.) led Cavendish to speculate that they were one and the same. The history of this is discussed here: http://ebooks.cambridge.org/chapter.jsf?bid=CBO9780511760013&cid=CBO9780511760013A009

Done.  Chzz  ►  07:36, 22 October 2011 (UTC)

Elemental molecular forms

I find the section "Elemental molecular forms" unsatisfactory in focusing mainly on the ortho/para physics, which is a curious detail, but indeed only little more than a detail (and is covered by its own page). IMHO this section should describe mostly (at an elementary level) the electronic structure of the H2 molecule, which is the simplest example of a covalent bond. It should explicitly refer to the Dihydrogen cation] page for details of the orbitals. I could volunteer to write something in this sense if the page gets unlocked to me. I am fairly expert in this field (see http://www.mi.infm.it/manini/). If someone more expert, e.g. a theoretical chemist, wishes to do it, I'd be more than glad to step back! Nicola.Manini (talk) 14:00, 8 November 2011 (UTC)

Freezing temperature

We have boiling, melting etc... Please can someone add freezing point. — Preceding unsigned comment added by 86.11.79.150 (talk) 15:26, 20 February 2012 (UTC)

We don't use the term "freezing point"; we use the term "melting point." It's the same point. Rklawton (talk) 18:08, 20 February 2012 (UTC)

N-ethylcarbazol

Perhaps N-ethylcarbazol can be mentioned that can be "charged" with hydrogen. See http://www.elektor.nl/nieuws/carbazol-elektro-benzine.1882087.lynkx 91.182.21.28 (talk) 13:57, 9 February 2012 (UTC)

characteristic of a hydrogen

what is a characteristic of a hydrogen-containing compound that determines its acidity. — Preceding unsigned comment added by 204.78.76.33 (talk) 16:54, 19 March 2012 (UTC)

The atom it is attached to must be sufficiently electronegative, with other electronegative atoms attached, in order to be able to spin off the proton.Jasper Deng (talk) 17:10, 19 March 2012 (UTC)

Natural occurrence

Under the heading of Natural Occurrence there is a sentence that implies that Jupiter has trace amounts of hydrogen in its upper atmosphere. "It has also been observed in the upper atmosphere of the planet Jupiter." However Jupiter's atmosphere is composed of 89% of hydrogen. — Preceding unsigned comment added by 206.127.180.1 (talk) 20:58, 22 April 2012 (UTC)

The sentence that you quoted does not at all—if anyhow—reference the amount of hydrogen in Jupiter's atmosphere, nor does it “impl[y] that Jupiter has trace amounts of hydrogen in its upper atmosphere.” It just says that it has “been observed in the upper atmosphere of ... Jupiter.” 71.146.19.40 (talk) 02:40, 30 April 2012 (UTC)

The antecedent of "it" in this sentence is trihydrogen molecular ion, anyway. I've rewritten it to make that more clear. SBHarris 00:18, 11 July 2012 (UTC)

Addition to Mettalurgy

Hydrogen is a concern in metallurgy as it can embrittle many metals, complicating the design of pipelines and storage tanks. With modern decision support tools the current risk is very low.

The first part is a true statement, but so is the second part, as the first statement targets pipelines for embrittlement, the addition comes from years of research published in 2009. So, whats wrong with it ? Mion (talk) 23:41, 10 July 2012 (UTC)

I can't parse the second sentence. What is "decision support tools"? Risk of what? (risk of embrittlement makes no sense to me because it is a continuous phenomenon). Materialscientist (talk) 23:45, 10 July 2012 (UTC)

Presumably some computer program into which you program alloys, exposures, temps, pressures, etc. Then it spits out a risk of failure. SBHarris 23:48, 10 July 2012 (UTC)

DST ref Mion (talk) 23:57, 10 July 2012 (UTC).

As for the risk on what, as the first statement is about the risk of embrittlement in steel, shouldn't the risk in the second statement reflect on that ? Mion (talk) 23:59, 10 July 2012 (UTC)

To me embrittlement is an important physical phenomenon related to hydrogen; risk of embrittlement makes no sense; risk of failure due to embrittlement does makes sense but is rather relevant to failure analysis than materials science; very low is also rather vague (and not scientific). Materialscientist (talk) 00:16, 11 July 2012 (UTC)

ok, so if we change risk to " the amount of embrittlement " ? the whole story about this part is that, as it used to be that embrittlement used to be a factor as it occured, the new situation is that with DST software, embrittlement occurs how it is controlled. Now should we leave that out, as it it part of modern material science ?. Mion (talk) 00:26, 11 July 2012 (UTC)

like "With modern decision support tools the chance of occuring embrittlement is low" ? Mion (talk) 00:32, 11 July 2012 (UTC)

Ah, I see. This is rather engineering - using materials science data to predict and improve performance of structural elements. It might be related to microscopic modeling of embrittlement (though your link doesn't make this impression), but then it would still be a metal topic, not hydrogen topic. Materialscientist (talk) 00:39, 11 July 2012 (UTC)

In that case you also have to remove the former sentence also, the one comes with the other, so you have to choose, i think. Mion (talk) 00:40, 11 July 2012 (UTC)

I don't think so - the first sentence is just a general introduction of hydrogen embrittlement and its importance for everyday life. Materialscientist (talk) 00:51, 11 July 2012 (UTC)

Well, the problem i have with the first sentence is "a concern" which is vague , and "complicating" which is vague too without a ref, so, i think the best solution is to add the both refs to the first sentence. Mion (talk) 01:03, 11 July 2012 (UTC)

Motor fuel template

Could someone logged in please add the { {Motor fuel} } template (I don't have my login handy). --85.134.53.70 (talk) —Preceding undated comment added 16:36, 20 July 2012 (UTC)

Done Mion (talk) 23:08, 14 August 2012 (UTC)

Edit request on 16 November 2012

Add an absolute electronegativitty of 7.18eV, in addition to the Pauling scale negativity.

Reference: J. Emsley, "The Elements," in The Elements, 3rd ed. New York: Oxford University Press Inc, 1998, ch 1, pp 98. (Reference uses IEEE referencing Classaccount073 (talk) 04:42, 16 November 2012 (UTC)

The Pauling scale is consistently used for other element articles. Our article on electronegativity suggests that there are at least five definitions of this property that have some validity but are only partially correlated with each other. Listing all five values might be excessive, however, and if any values were to be listed, they should be added to the articles of as many elements as possible, so that readers can compare. So I think a case would have to be made why we should have more than one value, and why that specific value rather than one of the other three. Samsara (FA • FP) 05:31, 16 November 2012 (UTC)

Two things missing

I think that the following two concepts whould be at least mentioned in this article (even more taking into account it is FA)

• Hydrogen batteries
• Hydrogen-powered vehicles

I'm saying this because I'm translating this article into Catalan and I want to help here as well.--Arnaugir (talk) 22:52, 22 November 2012 (UTC)

pKa of hydrogen

The Answer to the Ultimate Question of Life, The Universe, and Everything. Including the pKa of Hydrogen.

I'm trying to find the pKa of hydrogen as it is the conjugate acid of sodium hydride. However, I can't find a reliable source (searching for "pKa of hydrogen" infuriatingly reveals all sorts of irrelevant results, like the pKa of hydrogen sufide, hydrogen fluoride, basically every Bronsted acid). I want to add it to both the article for sodium hydride and this article. Can someone help me? 137.54.1.116 (talk) 03:45, 12 December 2012 (UTC)

The pKa of hydrogen H<sub>2</sub> is 42. [5]. This is also the answer to the ultimate question of life, the universe, and everything. [6]. So it all fits, you see. SBHarris 04:15, 12 December 2012 (UTC)

Why elemental hydrogen is rare on Earth

Because it's close to the Sun, is why! The excess hydrogen escaped Earth's gravity and was lost to space. Otherwise Earth would be like Jupiter, Saturn, Uranus and Neptune, with plenty of the stuff. The lede now says something patently untrue:

Naturally occurring atomic hydrogen is rare on Earth because hydrogen readily forms covalent compounds with most non-metallic elements and is present in the water molecule and in most organic compounds.

This suggests hydrogen is rare because the other elements soaked it up. But in the Solar System primordial cloud there was 75% hydrogen by mass and 2% of elements that could react with it, so that mechanism just won't work. There isn't enough of everything else (elements 3 to 92) to do the job. What happened was that the excess H2 simply escaped.

I'm writing this note because I've changed the lede to something correct in the past, and it's been changed back. So I'm going to do it one more time, and direct it to TALK. SBHarris 03:02, 20 April 2013 (UTC)

The new assertion is certainly uncited, certainly not in the body of the article, and I'm pretty sure it's wrong. The statement you quoted is correct; there is very little H that is in atomic (ie not in a molecule) form. It is also true that there are the fraction of H atoms in the Earth is much lower than in the Solar System as a whole, but that's a separate statement. This is discussed (more accurately than the revised lede) in Hydrogen#Natural occurrence. I'll clean up the lede with a partial revert. —Alex (ASHill | talk | contribs) 22:16, 20 April 2013 (UTC)

We don't care why there is little "atomic" H on Earth, as we don't expect atomic elements on planets, save for inert gases, as atoms are too reactive to stay separated. They bond to each other and all elements on Earth but a few rare inert gases are not atomic. We don't have to explain this any more than we have to explain why there are few Zebras at the South Pole. Why would we expect any? It's too cold for them even if they could get there. Less obvious than why there isn't much H on Earth is why there isn't much H2, when both H and H2 are common in the outer solar system.

For example, the atmosphere of Titan has several thousand times more H2 than Earth, and Titan's surface is covered in hydrocarbons (probably with ice below). And the atmospheres of Jupiter, Saturn, Uranus and Neptune have more H2 than any other gas (and the cores of Uranus and Nepture have more water than silicate). Earth's lack of H2 and lack of H compounds (which are much rarer here than on (say) Titan), needs explaining. We can't explain the lack of H2 by saying Earth's portion of H is all tied up on H compounds, because that isn't true. Earth should have far more H than we have H compounds. There is too much H2 in pre-solar clouds to be soaked up in other elements. Besides, silicates don't absorb H2.

The reason there is little H inside the asteroid belt is that H compounds are volatile inside the orbit of the asteroids and from smaller planets, they carry H into space. That is why the dinky little moon Europa has twice as much water on it as the entire Earth (and also twice as much hydrogen), with an ocean 60 miles deep. The Earth and the inner planets from Mars inward, are all hydrogen poor, even though it's the most common element in the Universe and the Solar System. And in comets. But in the inner solar system it doesn't collect onto objects because it's too hot.

Right now the lede says: Most of the hydrogen on Earth is in molecules such as water and organic compounds because hydrogen readily forms covalent compounds with most non-metallic elements. But that doesn't say why hydrogen is rare on Earth. Nor does reactive hydrogen explain rare hydrogen molecules on Earth, as the stuff would be rare even if non-reactive. If all the hydrogen on Earth were turned into H2, or if H2 were as non-reactive as He, H2 would still be rare on Earth as as a whole, and even in the crust. See abundance of elements in Earth's crust. Hydrogen, the most common element by mass in Sun and outer solar system, is 10th in abundance in Earth's crust, at 75% of the Universe's elemental mass, but something like 0.15% of the crust's mass (that includes ocean). That's ridiculously low and demands explanation. It isn't in the lede and it should be. SBHarris 01:40, 26 April 2013 (UTC)

OK, then how about finding a citation and incorporating the material into the body of the article, then dealing with the lede? —Alex (ASHill | talk | contribs) 04:56, 26 April 2013 (UTC)

Visibility of Hindenburg flame

The visibility of the flames of the burning Hindenburg is most likely due to the contamination of the hydrogen flame by hydrocarbons from the burning fabric of the airship. Plantsurfer (talk) 11:48, 20 April 2013 (UTC)

Yes. While low oxy H2 flames ARE visible, they look like high oxy natural gas flames, and are blue, never orange. Hindenburg was orange by all accounts, though no color photo exists, AFAIK. I have added a good ref with photo. SBHarris 18:50, 20 April 2013 (UTC)

Thanks, that is much better! Plantsurfer (talk) 18:55, 20 April 2013 (UTC)

Missing data, article structure

As the page is locked, I cannot commit any changes (besides I'm not an expert for most of them). Hopefully the following items could be handled by someone with the right permissions/knowledge:

1) Bond length of hydrogen should be listed somewhere(0.74 Å under normal conditions, I believe). Same for the binding energy. It might be a good idea to further expand on this subject (discrepancy in measured/theoretical bond length, difference in H covalent radius for H-H and H-X bonds with other X; dissociation T; also, do the different spin isomorphs have different bond lengths?)

2) "molecular forms" should ideally be a sub-subject of "phases" -- after all, gaseous/supercritical phase is the only one common, but right now it is not in the "phases" list.

3) "Crystal structure" entry is misleading - there is no "usual" solid phase and at least two (under normal pressure) low-T phases, one cubic fcc and the other hexagonal. Also, it would make sense to stress somewhere that the solid phases are NOT molecular, I think that's quite unusual for a diatomic gas.

4) Is the heat conductivity given for gas or for solid?

5) "oxidation state": H is indeed amphoteric, but I don't think it is an "amphoteric oxide"!!!

12.104.156.31 (talk) 18:45, 28 June 2013 (UTC)

On 5): it means that hydrogen oxide (aka water) is amphoteric. Agree it should be changed. "Oxide is amphoteric", maybe?

Your points are excellent, and I'm going to alert WP:ELEM (the main project+collaboration for this stuff which I'm part of) about this. Keep in mind though that the infobox template is used on all elements, so we try to keep it as general as possible. Double sharp (talk) 14:26, 29 June 2013 (UTC)

Heatured in hungaria Wikipedia

It's featured in huwiki, please somebody put the star! Thanks, 46.35.206.137 (talk) 18:36, 29 June 2013 (UTC)

Done. —Alex (ASHill | talk | contribs) 00:19, 30 June 2013 (UTC)

toxicity of hydrogen

anything CAN be toxic... & it just depends the creature your talking, the amounts & masses involved, the state of the creature... so many variables...

ya may get away with saying... 'not generally considered toxic to humans under many circumstances'

also i hav my doubts thr is not som rare, perhaps even sometimes obscure, maybe even unusual, hard t detect byproducts to the burning of hydrogen on large scales, on large scales & depending on the other chemicals involved n the ambient environment (i hate to use this word environment now, i hav to pause, try to come up with another term, it is so loaded from these battles between 'industrialists' & 'environmentalists', industrial is also now a loaded term, both political, the scientific accuracy cannot be understood anymore by most people that take sides on these political battles, they cant understand

anyways... gotta add an anyways, it may be able to form obscure reactions orcasionally, i havnt seen studys on it, & not that i am linking those to toxicity, but of course that all depends on the circumstances of the variables involved

Xenia Laboratorys — Preceding unsigned comment added by 74.87.136.238 (talk) 23:06, 31 July 2013 (UTC)

We are talking about human toxicity. There, hydrogen is as nontoxic as it's possible for a chemical to be. If you have evidence of toxicy, present it. Otherwise, the default is "nontoxic." SBHarris 02:28, 1 August 2013 (UTC)

Just to be a dick about it, if the available oxygen were at 3%, it would be rather lethal to humans if the remainder of the atmosphere present were hydrogen. To be serious about it, hydrogen is likely the most innocuous gas for humans imaginable, for any level that does not cause asphyxiation is well documented to cause no harm. That said, it can be an explosion hazard in significant concentrations. The only thing I can think of that would be more innocuous is helium. The data is trivially available, no toxic data, only data on reactivity, such as explosion hazard.Wzrd1 (talk) 02:35, 1 August 2013 (UTC)

Enthalpy

A seroius annoyance: It doesn't say what the bond enthalpy for H<sub>2</sub> is. For oxygen it says it is 498 kJ/mol (O<sub>2</sub>).--Solomonfromfinland (talk) 19:32, 22 August 2013 (UTC)

lifting gas

"it was once widely used as a lifting gas in balloons and airships"

As far as I know, the use of hydrogen as lifting gas has been increasing in recent years; the weather balloon lift gas market is estimated to be $200 million per year, and with helium becoming more expensive, helium users are switching to hydrogen. There are over a 1000 sites worldwide that do routine meteorological balloon/weather balloon launches, at least twice daily (at 0000 UTC and 1200 UTC). That's 750,000 launches per year for basic observations by the civil meteorological sector alone. Lifting gas application may seem of historical importance only, but replacing weather balloons with other technology would be much more difficult and costly than replacing the airships a century ago. Ssscienccce (talk) 00:05, 7 November 2013 (UTC)

Aldo prob basicly true that there is a shift to hydrogen coz of the helium costs, all currents sources only leed to a media hyped company which did 1 news release [[7]], we need an additional source about the size of the weather balloon market, maybe you can find one ? Cheers Mion (talk) 00:21, 7 November 2013 (UTC)

Neutronium?

Should we add this theoretical element before hydrogen? I feel like we should. The article is here: Elements Wiki And well as here: Neutronium... HumorousZR (talk) 02:35, 15 November 2013 (UTC)

Molecule

The article has almost no information about the molecule. What are its dimensions? What is its spectrum? How much energy to break it apart? All we have is information about the spin isomers. I find it hard to believe that this is a featured article with such incomplete coverage of the topic. There is not even a picture of the molecule. We could have hydrogen molecule or dihydrogen as a separate article rather than redirects as this article is big enough. Graeme Bartlett (talk) 02:21, 8 December 2013 (UTC)

Group

The infobox indicates that hydrogen is in Group I. H is often stuck in that location in the periodic table. Other times it is placed with Group VII or off on its own somewhere. It is not normally considered to be a Group I element, which is restricted to the alkali metals. Ordinary Person (talk) 03:01, 30 September 2014 (UTC)

Nope...the alkali metals and group 1 are two different sets. IUPAC makes it pretty clear in the Red Book that hydrogen is a group 1 element, but not an alkali metal. Double sharp (talk) 04:34, 30 September 2014 (UTC)

Expansion of section on production

This should include something on electrolysis which is the second most common way of producing hydrogen after thermo-chemical routs such as reforming or gasification. There is a good section on the hydrogen production page. — Preceding unsigned comment added by Just Chris 1 (talk • contribs) 06:04, 23 October 2014 (UTC)

Possible addition

There are two distinct reactions in which 4 H atoms may eventually result in one He atom. The first of these is:

1.i)	1H	+	1H	→	2D	+	e+	+	ν
1.ii)	2D	+	1H	→	3He	+	γ
1.iii)	3He	+	3He	→	4He	+	1H	+	1H

This reaction sequence is believed to be the most important one in the solar core. The total energy released by these reactions in turning 4 Hydrogen atoms into 1 Helium atom is 26.7 MeV. The second reaction generate less than 10% of the total solar energy. This involves carbon atoms which are not consumed in the overall process. The details of this "carbon cycle" are as follows:

2.i)	12 C	+	1H	→	13N	+	γ
2.ii)			13 N	→	13C	+	e+	+	ν
2.iii)	13 C	+	1H	→	14N	+	γ
2.iv)	14 N	+	1H	→	150	+	γ
2.v)			15 O	→	15N	+	e+	+	ν
2.vi)	15 N	+	1H	→	12C	+	4He	+	γ

References

Comments

Add comments here. Headbomb {talk / contribs / physics / books} 06:02, 29 August 2014 (UTC)

Black Light Power hydrogen theories should be included?

I think that there should be some inclusion of the "hydrino" theory that BLP claims is true, not because it is (and it's plain to see why), but because it's one of the more well-known controversial pseudo-scientific theories. Thanks, DasПиg <sub>talk</sub> 22:37, 11 January 2015 (UTC)

Probably not in this article as it would be WP:undue detail. It would not help people understand hydrogen. Graeme Bartlett (talk) 06:52, 13 January 2015 (UTC)

Directly relate to 1H2 for the physical properties in the infobox

The infobox gives information for 1H such as standard atomic weigh 1.008(1). The physical properties there however all related to 1H2. I suggest to modify the caption to "Physical Properties (^1H_2)" and add also Molar Mass to the section. For consistency that should be done for other gases as well (e.g. oxygen). (Sheliak (talk) 23:58, 20 January 2015 (UTC))

74% of the Elemental Mass of this Universe is Hydrogen

A google search produces many reliable sources agreeing that "74% of the elemental mass of this universe is hydrogen". College textbooks also state this. This article needs to be more accurate. - Omnireligious (talk) 00:59, 30 January 2015 (UTC)

State your sources. Yahoo Answers? LOL. The present article says 74%. The metallicity article here (with its own sources) says 73%. Best guess for helium is 25% [8], which puts H at 73%. SBHarris 02:04, 30 January 2015 (UTC)

Sock of a rather off-the-wall editor. Dougweller (talk) 14:38, 18 February 2015 (UTC)

Flammable or Inflammable Air

This article mentions Cavendish calling his discovery of hydrogen as "flammable air". Everywhere else that I've seen that talks about Cavendish and phlogiston theory, uses the term "inflammable air." 75.150.48.86 (talk) 16:45, 26 March 2015 (UTC)

inflammable is here [9], but following the usage notes here [[10]] it is flammable to prevent confusion.Mion (talk) 18:09, 26 March 2015 (UTC)

In this context the article is describing the history of hydrogen specifically what Cavendish named his discovery. It seems to improper to change the words he used. The wikipedia page on Cavendish [[11]] uses the term "inflammable air".72.219.204.154 (talk) 23:33, 31 March 2015 (UTC)

Hydrogen as element vs. hydrogen as molecule

This article is confusing, it mixes element, and molecule. I think it should be splited up like in Spanish wikipedia (Hidrógeno/Dihidrógeno), and other elements that are not found free (O,O<sub>2</sub>,O<sub>3</sub>). It would be hard to students get the difference if you put it in the same article and jump to one and to another without saying so.

Some differences:

Property	Applies to H	Applies to H2
Symbol	YesH	No
Formula	YesH	YesH2
Name	YesHydrogen (element/atoms)	YesDihydrogen/Hydrogen gas
Atomic number	Yes	No
Mass	Yes (atomic mass=~1)	Yes (molar mass=~2)
Found free on Earth	No, found bonded to same (=>H2) or other elements (=>H2O, H4C, etc.)	Yes
Form compounds	Yes	No

Eloy (talk) 21:49, 2 April 2015 (UTC)

I would still recommend that this article covers basic information about the molecule. But more detailed information could go into another page called dihydrogen or hydrogen molecule. We already do have a more detailed article on Hydrogen atom and the exotic trihydrogen. Graeme Bartlett (talk) 05:30, 19 May 2015 (UTC)

Other information missing includes physical properties such as viscosity, thermal conduction, electrical conduction, critical point, dielectric constant, density over a range of pressures - phase diagram, magnetic properties. Hydrogen as an atmosphere in a star or a planet has much written on the topic, and should have an article linked. This leads to wanting to know its appearance in bulk, and in different conditions. Other uses missing are NMR itself, and manufacture of margarine. So perhaps some should go in here and some in other article(s) on the molecule. Graeme Bartlett (talk) 21:35, 20 May 2015 (UTC)

Minor cleanup

While looking through our older FAs, I noticed a few minor issues here. I fixed a bare url in the references, and removed an external link that no longer functioned. Appreciate if someone would take a shot at replacing the 4 deadlinks, and eliminating unnecessary "See also" links (many of them are already linked within the article, some quite prominently). Thanks. Maralia (talk) 04:40, 19 May 2015 (UTC)

I've also added a few {{better source}} tags, and a handful of {{full citation needed}} tags. Will try to help out with these. Maralia (talk) 15:06, 19 May 2015 (UTC)

I have addressed and fixed all these issues. And removed an undue section on xylose. Graeme Bartlett (talk) 22:05, 20 May 2015 (UTC)

Great work—thank you Graeme! Maralia (talk) 22:45, 20 May 2015 (UTC)

Hydrogen reference 120 links to EU food article and not one described in reference.

I am new to this, but I wanted to point out that reference 120 points to the incorrect article. I am not certain how to fix it.

Thank you,

66.188.202.17 (talk) 12:17, 30 September 2015 (UTC)

Fixed. Thanks for the note. It's a rather old source and the research appears incomplete. Could you suggest a paper published after the project was completed? Jim1138 04:41, 1 October 2015 (UTC)

Our Sun contains ~74% hydrogen

Our Sun contains ~74% hydrogen should be added to this article. It's in the Sun article. 2601:589:4705:C7C0:CD39:BFB6:B7C2:56F0 (talk) 15:47, 23 October 2015 (UTC)

The Sun article says 74.9% (which is rounded to 75%, not 74%), citing [12]. Gap9551 (talk) 17:09, 25 October 2015 (UTC)

That source is rather old though. Do you know of recent scientific papers (preferably peer reviewed) improving on this figure? Gap9551 (talk) 17:16, 25 October 2015 (UTC)

74% of this Universe's elemental mass is Hydrogen

It's very important to be as accurate as possible. http://pdgusers.lbl.gov/~pslii/uabackup/big_bang/elementabundancies/2300400.html . — Preceding unsigned comment added by 69.180.104.60 (talk) 16:28, 1 August 2015 (UTC)

MODERATORS. This should be tweaked. Our Sun contains ~74% hydrogen SHOULD BE ADDED. 2601:589:4705:C7C0:CD39:BFB6:B7C2:56F0 (talk) 15:45, 23 October 2015 (UTC)

The article currently says this: Hydrogen, as atomic H, is the most abundant chemical element in the universe, making up 75% of normal matter by mass. Are there recent scientific sources that say 74% for the Universe? Then we could change it. Gap9551 (talk) 17:14, 25 October 2015 (UTC)

Abundances of H in stars and planets (other than the Earth) may be beyond the scope of this article focusing on hydrogen. The Universe as whole is a different matter though. Gap9551 (talk) 17:27, 25 October 2015 (UTC)

In 2007, it was discovered ...

... that an alloy of aluminium and gallium in pellet form added to water could be used to generate hydrogen.

Not true: the fact "discovered in 2007" was described in chemistry handbook printed in 1956 (Tołłoczko, Kemula "Chemia nieorganiczna", XI edition, PWN Warszawa 1956, p. 540); unfortunately there is no information, when the reaction was discovered - possibly much earlier.

JerzyTarasiuk (talk) 23:49, 22 November 2015 (UTC)

Offending text snipped. Graeme Bartlett (talk) 05:21, 23 November 2015 (UTC)

There was some information available at the time. This is incorrect. — Preceding unsigned comment added by 2600:1010:B066:817D:A875:E909:F498:6910 (talk) 22:58, 4 September 2016 (UTC)

D/T

why would the symbol for hydrogen be D or T? 108.66.234.9 (talk) 01:14, 3 November 2016 (UTC)

I have no idea; those are just isotopes of hydrogen, not special elements. The interesting variant of the question is why those isotopes have special names but no isotope of any other chemical element has a special name. Georgia guy (talk) 13:45, 3 November 2016 (UTC)

Since you've responded to this, I'll refrain from deleting this troll question that is clearly intended to waste people's time, since this is already in the article (and, what do you know, the editor is posting this on the right article instead of symbol (chemistry), indicating that s/he knows the answer already, and has been disrupting the extended-periodic-table articles for ages). The reason why only the hydrogen isotopes have separate names is that it is only for them that the difference in mass is large enough (100% for H vs D) to cause easily observable effects. For instance, if you live on a diet solely involving the <sup>13</sup>C isotope, nothing will happen to you. If you attempt to substitute all your protium with deuterium, you will die. Double sharp (talk) 13:53, 3 November 2016 (UTC)