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Topic: how come "noble gases" like xenon, krypton and radon form compounds  (Read 15999 times)

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Offline antimatter101

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I just came across the molecule xenon tetrafluoride and found it weird. Xenon is a noble gas, with a stable shell so it is unreactive, but it still forms compounds. I also looked at the pauling electronegativity scale. There was no electronegativity for helium, neon and argon because they didn't form compounds so the electronegativity cannot be measured, but there were units for krypton, xenon and radon. Can someone help me?

Offline Schrödinger

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Re: how come "noble gases" like xenon, krypton and radon form compounds
« Reply #1 on: October 12, 2012, 06:28:55 AM »
Fluorides of Xenon have been reported. http://en.wikipedia.org/wiki/Xenon_fluoride. They certainly are inert gases, but when a very strong oxidizing agent like fluorine is used under harsh conditions, it gets oxidized.

Pauling electronegativity is calculated using the bond enthalpies of the certain coumpounds. (see : http://en.wikipedia.org/wiki/Electronegativity, read under Pauling electronegativity). Since compounds of Xe , etc are known, people probably calculated electronegativities from data pertaining to them like bond dissociation, etc.
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Offline SapereAude1490

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Re: how come "noble gases" like xenon, krypton and radon form compounds
« Reply #2 on: October 12, 2012, 06:50:30 AM »
When people were making O2PtF6 from PtF6 and O2, they found out(using X-rays) that the compound O2PtF6 was made up of O2+ ions and PtF6- ions.

The ionization energy of O2 is 12,2eV and of Xe 12,1eV so they tried Xe instead of O2. When they tried mixing dark red PtF6 vapors with excess Xe at room temperature, a solid yellow Xe+PtF6- was formed.

Also, Xenon's outer shell is 5s25p6. The energy difference between these higher quantum states orbitals is small, so you can take a few of these electrons and place them in 5d-orbitals, like this


5s     5p       5d
:spinpaired:    :spinpaired: :spinpaired: :spinup:    :spinup:

or

:spinpaired:    :spinpaired: :spinup: :spinup:    :spinup: :spinup:

Offline EpicWinston

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Re: how come "noble gases" like xenon, krypton and radon form compounds
« Reply #3 on: October 12, 2012, 09:53:02 AM »
I was thinking the same thing while taking general chem. It is important to realize this does not happen naturally. The conditions must be harsh, extremly harsh. Another thing to take into perspective is periodic trends. F is extremly elctronegative, Xe is kinda big (electrons are further apart, so they are not as attracted to the nucleus), so if an inert gas was going to react (Under harsh conditions) with any other element wuldn't these two be a good match? 

Offline antimatter101

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Re: how come "noble gases" like xenon, krypton and radon form compounds
« Reply #4 on: October 12, 2012, 10:21:42 PM »
Thanks! SpareAareDUDE you rock! I gave you an extra mole snack!

Offline antimatter101

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Re: how come "noble gases" like xenon, krypton and radon form compounds
« Reply #5 on: October 12, 2012, 10:38:12 PM »
Wait a minute, what is the structure of O2PtF6?

Offline SapereAude1490

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Re: how come "noble gases" like xenon, krypton and radon form compounds
« Reply #6 on: October 13, 2012, 11:54:20 AM »
I have no idea... (goes off to Google it)

Found this http://jcp.aip.org/resource/1/jcpsa6/v44/i5/p1748_s1?isAuthorized=no

Apparently, you can't use electron diffraction to figure out the structure ... strange. I thought you use neutron diffraction to see small molecules like Hydrogen. I guess I have a lot more to learn...  :)

They also say "The PtF6- ion is a regular octahedron with a Pt☒F bond length of 1.82±0.03 Å."

So it's like http://upload.wikimedia.org/wikipedia/commons/0/07/Octahedron.svg, with the Pt atom inside it.

The O2+ bond to PtF6- is ionic. Same thing with Xe+. That F really can't get enough of electrons. What a selfish prick of an element...

As EpicWinston said, F is extremly electronegative. So if it can take an electron from O2, it can take it from Xe too.

Also I forgot to say that in Xe


5s     5p       5d
         
 :spinpaired:   :spinpaired: :spinpaired: :spinup:   :spinup:
and

 :spinpaired:   :spinpaired: :spinup: :spinup:   :spinup: :spinup:
           

The first one makes two covalent bonds and the second one four.

In Xe+ it's probably the first case where you have two unpaired electrons and one electron is being pulled away more than usual by fluorine, making a cation. The other one is covalent? Don't have a clue really. Maybe it just stays in the Xe p-orbital, making the whole thing paramagnetic, or not. I'll see what I can find.

Offline antimatter101

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Re: how come "noble gases" like xenon, krypton and radon form compounds
« Reply #7 on: October 14, 2012, 12:20:27 AM »
Thanks! Another mole snack... tomorrow.

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Offline SapereAude1490

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Re: how come "noble gases" like xenon, krypton and radon form compounds
« Reply #8 on: October 14, 2012, 06:29:12 AM »
Yeah, yeah.

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