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helen-louise
baratron
baratron
I have spent far too long chasing wild geese tonight
Does anyone want to prove their superior Google-fu? According to one of my databooks, the lattice enthalpy of tin (IV) oxide is in the order of 11000 kJ mol^-1. Theory suggests that tin (IV) oxide should have a high lattice enthalpy because of being made of +4 and -2 ions, but that number is severely off the scale. The highest lattice enthalpy I know of is magnesium oxide, which is around 3800 kJ mol^-1 (although apparently beryllium oxide is ~4500 kJ mol^-1). I cannot find anything to prove if that's a typo or not. My other textbooks are obsessed with Group 1 & 2 compounds.

I don't actually need to know this, but now that the question's been raised, I won't be happy until I find out.

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From: hattifattener Date: 28th March 2008 02:57 (UTC) (Link)
Its melting point is either 1127 C or 1600 C, depending on which web pages you believe. (My CRC handbook is packed.) My chemistry-fu is quite weak but can't you estimate the crystal enthalpy from the melting point?
brooksmoses From: brooksmoses Date: 28th March 2008 04:31 (UTC) (Link)
My CRC handbook isn't!

And it says that Sn2O has a lattice energy of 11807 kJ mol^-1.

This is, mind you, nowhere near off the scale -- around 40% of the oxides (some three dozen of them, roughly) are in that range. The highest is Al2O3, at 15916, but Ga2O3 at 15590 is close, and Cr2O3, Mn2O3, and V2O3 at 15276, 15146, ann 15096 respectively aren't far behind either.

This also confirms your numbers for MnO and BeO, roughly -- 3724 and 4293, respectively. It's interesting that these seem to fit into two general categories -- there are the M2O3 oxides, which are all higher than 12000, and a bunch of the MO2 oxides in the 10000-12000 range, and then the MO oxides in the 3000-4000 range, the M2O2 oxides in the 2000-3000 range, the rest of the MO2 oxides in there as well, and the M2O oxides from 3000 down to 700ish.

Edited at 2008-03-28 04:36 (UTC)
brooksmoses From: brooksmoses Date: 28th March 2008 04:40 (UTC) (Link)
In high lattice energies for non-oxides, there's TiF4 at 10012 and a dozen or so similar halides near that, and ThB6 and CeB6 at 10167 and 10083, with a dozen similar borides around 7500.

Weakest listed, meanwhile, is Bu4NHCl2 at 290.
baratron From: baratron Date: 28th March 2008 22:37 (UTC) (Link)
Thank you! I'd been hoping that someone with access to the "proper" edition of the CRC Handbook would comment. Richard has a student edition, which is still extremely thick and appears to have lots of content, but has absolutely no useful indexing. The pages are in a very random order and many of the tables look like they haven't been altered from when they were originally typeset in 1910 or whatever. It's pretty much unusable for anything other than looking up data for organic compounds, as there are SO MANY pages of those that it's impossible to miss them all!

11807 kJ mol^-1 is off the scale in comparison to Group 1 & 2 oxides & halides though! Especially if it's the only non-s block compound in your data book (why that one? I have no idea). I didn't know that lattice enthalpies could get that high, let alone that aluminium oxide should be so much higher than magnesium oxide. I might have to add relearning crystal structures to my list (*shudders slightly*, as I am extremely bad at visualising 3D).

I wonder why the M2O3 oxides should be higher than the MO2 ones? M2O3 has +3 and -2 ions, whereas MO2 has +4 and -2... but fewer ions in total. Wonder if the total charge is an issue?
brooksmoses From: brooksmoses Date: 29th March 2008 02:57 (UTC) (Link)
Would you like a copy of the proper version? The local library booksale seems to have them pretty regularly for $5 or so for ones from the mid-1980s or so (which that was). Getting it to you might be a bit complicated, though, but I'd be quite willing to put one in a cheap book-rate shipment or suchlike.

The tables do tend to be somewhat in random order even in the proper ones, but at least it's got a decent index, and usually has bibliographic notes on where the data came from, even if the typesetting is uneven.

I wouldn't think the total charge as such would be the distinguishing thing, since in a crystal the fact that we call it MO2 instead of M2O4 is arbitrary human terminology rather than the underlying physics. I'd guess it has something to do with packing densities or something in the lattice structure, but I really have no idea. :)
From: (Anonymous) Date: 29th March 2008 04:10 (UTC) (Link)

Magnesium Oxide

Magnesium oxide is such interesting stuff and almost unknown in the States as a building product. We are importing some to use as wallboards, as a sheetrock replacement in this Gulf coast hurricane proof house. http://www.ConcreteCottage.com

I am always interested when people are discussing MO2 as I find little about it in English language websites.
Lundy
baratron From: baratron Date: 30th March 2008 19:56 (UTC) (Link)

Re: Magnesium Oxide

Well, if you're looking for magnesium oxide and thinking it's MO2, that's your problem there. Magnesium oxide is MgO.
baratron From: baratron Date: 30th March 2008 19:57 (UTC) (Link)
Huh. Yes, I would like one, but the postage will be a killer. I suppose if you sent it surface mail rather than air mail, that might help?
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