Sciencemadness Discussion Board - Theoretical chemistry of sulfur

Theoretical chemistry of sulfur

bismuthate - 30-11-2013 at 05:01

Chlorates, bromates, and iodates are all possible because oxygen is more electronegative than the respective halogens and are capable of being oxydised by oxygen (I believe). Sulfur behaves much like oxygen and can usualy form compounds where it is in the place of oxygen, but it cannot do this with the halogens because they are more electronegative than it. Recently I found the astatine is less electonegative than sulfur! So I wondered would an ion be possible that is like an astatate except with sulfur in the place of oxygen?
(Sorry if this belongs in beginings. Feel free to move it there.)

[Edited on 30-11-2013 by bismuthate]

[Edited on 30-11-2013 by bismuthate]

blogfast25 - 30-11-2013 at 06:42

There's a mention of Astatine (note spelling) compounds with sulphur in Wiki.

gsd - 30-11-2013 at 06:47

The only problem is availability of Astatine.

TTBOMK it is one of the rarest of rare elements. Following quote is from webelements website:

Astatine is not found in any significant quantity in the geosphere. Some isotopes of astatine (215At, 218At and 219At) are present in uranium and thorium minerals as part of radiodecay series. The total amount present in the Earth's crust is probably less than 30 g at any one time.

gsd

homeIandsecurity - 30-11-2013 at 06:51

Astate does exist!
But the answer is 'no'. Because 'ate' means largest number of oxygen (not sulfur) atoms in anion with that compound. There are lots of '-ate' anions: nitrate, sulfate, chlorate, nickelate, palladate, aurate, bismuthate (i saw this user here), phosphate, iodate, bromate, ferrate, aluminate, zincate, gallate, rhodate, rhenate, fluorate, argentate, molybdate, manganate...

bismuthate - 30-11-2013 at 06:52

gsd, that is why it's theoretical chemistry.
blogfast25, I saw and I found it interesting, but what I was thinking about was the possibility of the AtS3- ion or compounds like NaAtS3. Also sorry about the spelling I don't know why I instictivly spell it that way.
homelandsecurity there's thiobismuthate, thiocarbonate, and many more.

[Edited on 30-11-2013 by bismuthate]

blogfast25 - 30-11-2013 at 08:01

Quote: Originally posted by bismuthate

blogfast25, I saw and I found it interesting, but what I was thinking about was the possibility of the AtS3- ion or compounds like NaAtS3. [Edited on 30-11-2013 by bismuthate]

Well, just because Wiki doesn't mention it doesn't mean it can't exist of course. Your thioastatate suggests an oxidation state of V. If a (for now hypothetical) At2S5 could exist then chances are that a thioastatate V could exist too. I doubt if that is possible though, because S isn't (I think) electronegative enough.

Wiki mentions for polonium (somewhat similar to At) a monosulphide (presumably PoS). Perhaps an At2S can be imagined? From which a hypo thioastatate, AtS-, could be envisaged? All pure speculation of course...

Quote: Originally posted by homeIandsecurity

Astate does exist!

Astatate, like chlorate, bromate etc. Not 'astate'.

[Edited on 30-11-2013 by blogfast25]

bismuthate - 30-11-2013 at 08:41

Well At has an electronegativity of a mere 2.2 acording to wiki while S has an electronegativity of 2.58! This is a decent difference between the two (more than the difference between Cl and O). My theoretical preperation would be to mix an excess of astatine with sodium hydrosulfide and heat. The reaction would go like this:
6At+6NaHS==>5NaAt+NaAtS3+3H2S
Very much the same way that chlorates are produced.

blogfast25 - 30-11-2013 at 10:44

Electronegativity is far from the only thing to consider here. Also, for a given element it increases with the oxidation state of the atom. The values you quote could be called the 'first electronegativity', but they say precious little about Astatine's willingness to share a second, third etc electron with sulphur atoms.

Much the same way chlorates are produced? I'd say it couldn't be more different!

[Edited on 30-11-2013 by blogfast25]

bismuthate - 30-11-2013 at 10:50

It was replacing the O with S and the Cl with At in the reaction. I couldn't find the other electronegativity values, but I found wiki states it has a V oxidation state.
I can't find the 2nd ionization energy.
[Edited on 30-11-2013 by bismuthate]

[Edited on 30-11-2013 by bismuthate]

blogfast25 - 30-11-2013 at 11:40

Quote: Originally posted by bismuthate

I can't find the 2nd ionization energy.

You won't, nor would it be particularly useful. The (oxo) astatates would be held together by bonds somewhere between covalent and ionic. See for instance the structure of the chlorate anion.

Quote: Originally posted by bismuthate

It was replacing the O with S and the Cl with At in the reaction.

Simply replacing atoms by others on a piece of paper has nothing to do with "production". There's only so far simple analogies can take you.

Going back to electronegativity, that concept is best used for predicting whether certain simple binary compounds are likely to form and what will be the nature of the chemical bond between the atoms. a simple At-S bond is likely to be polarised with a partial negative charge on the S atom and a partial positive charge on the At atom. But that doesn't imply more complicated arrangements will be viable.

[Edited on 30-11-2013 by blogfast25]

bismuthate - 30-11-2013 at 11:48

Ok. Well is there a way to calculate 2nd-5th electronegativity?

[Edited on 30-11-2013 by bismuthate]

blogfast25 - 30-11-2013 at 11:53

Quote: Originally posted by bismuthate

Ok. Well is there a way to calculate 2nd-5th electronegativity?

[Edited on 30-11-2013 by bismuthate]

Possibly but that won't really help you out either. It's too reductionist.

bismuthate - 30-11-2013 at 11:57

Is there another way to find out if compounds are possible?

blogfast25 - 30-11-2013 at 12:05

At the end of the day it boils down to whether the compound has a negative ΔG (Gibbs Free Energy) of Formation or not. If ΔGFormation < 0 the compound is stable and will not spontaneously fall apart. ΔGFormation is itself a sum of various terms, some of which may be negative, others positive.

To get an idea of the complexity, look at the Born-Haber Cycle for simple (binary) ionic compounds:

http://www.wyzant.com/resources/lessons/science/chemistry/bo...

And this doesn't even tell you anything about Entropic effects: ΔG = ΔH - TΔS

bismuthate - 30-11-2013 at 12:36

Some how I'm doubting I'll be able to find all the needed info on astantine.

blogfast25 - 30-11-2013 at 13:36

Quote: Originally posted by bismuthate

Some how I'm doubting I'll be able to find all the needed info on astantine.

That's a safe bet.