Talk:Tungsten hexafluoride

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Correction: Tungsten hexafluoride is not the densest known gas, that prize goes to uranium hexafluoride. Physchim62 15:54, 24 May 2005 (UTC)

Uranium hexafluoride is a volatile solid; it sublimes at 56.5 ˚C. So at room temperature, tungsten hexafluoride is still the densest "gas". The solid UF₆ would almost certainly exist in equilibrium with some vapor, so depends on what you consider gas. --71.227.190.111 03:54, 31 July 2006 (UTC)

Semiconductor industry

"The dominant application of tungsten fluoride is in semiconductor industry" well, even if only a minor part of the tungsten carbide is manufactured through the tungsten hexafluoride process this would probably be a more important application at least by volume. —Preceding unsigned comment added by 150.227.15.253 (talk) 08:30, 27 July 2010 (UTC)

Corrections

Tungsten hex is a water white colorless liquid. If it is contaminated with Cr then it is yellow to orangish red depending on how much Cr and which Cr speicies is contaminating it. It will form HF on contact with water and it will cause damage, not may. 24.229.244.111 17:10, 11 February 2006 (UTC)

Not a gas?

Tungsten hexafluoride is not a gas at standard conditions. STP for gases is defined as 0° C and 1 atm. The standard boiling point of this compound is listed as 17.1° C. It is a gas at room temperature, but not at standard temperature. 144.162.23.122 (talk) 22:27, 24 September 2013 (UTC)

Good point. Maybe, the standard conditions should actually be linked to standard state, in which tungsten hex would be a gas. Hopefully someone can clear this up. Piguy101 (talk) 00:30, 9 April 2014 (UTC)

Comments

• Well, I guess that the prize for the most dense gas could become legalistic, depending on conditions and the degree to which one wants to discuss transient species and plasmas, but by most normal perspectives UF6 is probably it. I dont know if perfluorides are known for the still heavier elements such the congener of W.
• Back to the WF6 report. It is claimed to be "odorless". Thus, the rate of hydrolysis must be quite slow, because I would expect it to smell like HF.
• Also, I propose to replace the tentative "may"s in the following quote, fix the awkward which ( implying that water can penetrate...), and remove the claim that WF6 can damage bone (seems silly)

"WF6 may form hydrofluoric acid (HF) on contact with water, which can penetrate the skin and cause damage to the subdermal tissues and bone. Inhalation may cause respiratory tract burns and can be toxic. This compound is a lachrymator which causes tearing and irritation of the eyes. Contact may cause burns to the eyes, skin and mucous membranes." One question is whether WF6 poses dangers beyond being an in situ source of con HF. Smokefoot 17:44, 11 February 2006 (UTC) I have physically seen WF6 react instantly with the moisture in the air to form a smokey white cloud. As for its odor, I am glad I don't know what it smells like! (24.229.244.111 02:54, 15 February 2006 (UTC))

Synthesis

The statements made about its synthesis do not make much sense and seem to be circular. Besides the reference is not very satisfactory because it is a patent about its use rather than its synthesis and only the abstract seems open to scrutiny. Jcwf (talk) 03:43, 20 November 2008 (UTC)

I attempted to address this gap about the prep and gave more general refs. It is made by direct fluorination.--Smokefoot (talk) 04:55, 20 November 2008 (UTC)

everything heavier than WF6 is not gaseous

Is there some reason why this must be? I mean some theoretical calculations which support this observation in an elementary way? In the theory of ideal gases, the molar mass of the molecule does not play a role, it is just characterized by the lack of strong intermolecular forces. Or is it just observation? There are some other candidates which are possibly gaseous at standard conditions, and which would be heavier than WF₆, e.g. Uuo or SgF₆. But on the other hand, all of them are strongly doubted to be gaseous - due to relativistic effects, or due to some "law" which says they are too heavy? --79.243.242.143 (talk) 14:02, 7 September 2013 (UTC)

Uuo (which I will refer throughout the rest of this post as element 118 or E118) – we really do not know. A simple extrapolation from the rest of the noble gases gives you a boiling point of 80 °C(!), which would make it a solid. A less recent (but relativistic) source calculates the melting and boiling points respectively to be −15 °C and −10 °C respectively, which would make it gaseous. I still think it could reasonably be a gas. I'm not quite sure about the reasons for this calculation (but I will try to find out). But note that WF₆ has a molar mass of about 298 g/mol, just beating element 118 at 294 g/mol, so this would not count in any case.

SgCl₆ is expected to be stable and somewhat volatile, though still solid at STP. So SgF₆ might be gaseous too, or perhaps an even more volatile solid. But this is unreferenced speculation (I looked; there doesn't seem to be speculation on SgF₆, just SgCl₆ and SgBr₆). Also note that this book is somewhat old (2004) already and thus states CnF₄ and HgF₄ to be unlikely to exist (completely opposite to current thinking and the synthesis of HgF₄!), so I would be cautious.

TL;DR: The most likely candidates for heavier gases involve superheavy transactinide elements, which is why WF₆ is the heaviest substance experimentally observed to be gaseous at STP. But there is probably no law preventing it. Double sharp (talk) 04:50, 8 September 2013 (UTC)

Another possible "candidate" for a heavier gas is AtF₇, but this case seems to be even less clear, since only one lighter homologue - IF₇ - is known, and scientists are not sure if astatine is even able to display the oxidation state +7. --79.243.250.21 (talk) 19:54, 8 September 2013 (UTC)

What about W(C_nH_2n+1)₆. They must be heavier than WF₆, if n > 1. We can think about similar organometallic compounds of Po, At, Sg etc..--Anoop Manakkalath (talk) 09:42, 1 April 2014 (UTC)

Sorry for thread necromancy, but I have found a blog from someone who has dived into the issue of "the densest gas under standard conditions" a bit deeper:

https://eugenebo.wordpress.com/2017/01/11/13-heaviest-gases/

There, polonium hexafluoride is mentioned as the most likely candidate beating WF₆. The problem is that it is very poorly characterized, and even the most stable ²⁰⁹PoF₆ is a nigh-impossible job due to autoradiolysis and the small quantities of ²⁰⁹Po that are experimentally accessible. (Which would also mean that AtF₇ and SgF₆ barely stand a chance to get characterized well enough to even roughly guess their experimental boiling points.)

Besides, Ge(CF₃)₄ is mentioned as being a "near miss" with a boiling point just over room temperature. So maybe its lighter congener Si(CF₃)₄ (molecular mass 304) might be gaseous at STP? My own private literature research on that came up inconclusive, since that compound, too, is hardly characterized. However, the even lighter C(CF₃)₄ (perfluoroneopentane) is predicted to be liquid, or even solid, at STP with a boiling point around 35-40°C. So we will only know when somebody has synthesized Si(CF₃)₄ in good enough quality and quantity to measure its melting and boiling points. Same for PoF₆, AtF₇ and SgF₆, except that these have the additional issues of autoradiolysis and radioactive decay.

Long story short, it appears WF₆ is the densest gas under STP that is known with good certainity to be a gas. Everything beyond that right now is highly speculative and mostly original research. --2003:E7:7707:441:E507:5BA2:2DFF:2862 (talk) 05:35, 18 January 2022 (UTC)

Assessment comment

The comment(s) below were originally left at Talk:Tungsten hexafluoride/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

Too short for A-Class. Wim van Dorst (Talk) 23:12, 10 February 2007 (UTC).

Substituted at 18:10, 5 June 2016 (UTC)