expanded octet XeF4

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804991762_4A
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expanded octet XeF4

Postby 804991762_4A » Fri May 11, 2018 10:57 pm

Can someone clarify as to why in XeF4, you cant make a double bond, instead of having 2 lone pairs?
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Valeria Viera 1B
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Re: expanded octet XeF4

Postby Valeria Viera 1B » Fri May 11, 2018 11:15 pm

it's because F it does not follow the rules to have an expanding octet meaning that it is not possible for F to take anymore electrons since it is in the second row (elements from third row and down can get expanding octets from d orbital)

Shimran Kumar 1C
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Re: expanded octet XeF4

Postby Shimran Kumar 1C » Fri May 11, 2018 11:17 pm

There explanation was that if you found the formal charges for the structure with and without double bonds, the one without would have charges closer to 0 and thus be the better structure for the molecule.

Steven Luong 1E
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Re: expanded octet XeF4

Postby Steven Luong 1E » Sun May 13, 2018 2:34 am

Assuming you found the formal charges of both the normal structure and one with double bonds, the structure with 2 lone pairs (normal) will have a lower energy state than the one with double bonds, which is more appropriate. However, you can also explain this with the fact that Fluorine is in the 2nd row (2nd energy level). It can only fill itself with 8 electrons max because of the p orbital. Since F cannot expand into the d orbital because of its nature as a 2nd energy level element, it cannot acquire more than an octet of electrons.

Chem_Mod
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Re: expanded octet XeF4

Postby Chem_Mod » Sun May 13, 2018 3:11 pm

F cannot have more than 8 electrons. F cannot have an expanded octet

Chris Qiu 1H
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Re: expanded octet XeF4

Postby Chris Qiu 1H » Sun May 13, 2018 3:16 pm

The expanded octet rule can only apply to elements on the third row of the periodic table or higher due to the presence of the D-orbitals. Florine does not fit those criteria so there is only one option for the extra electrons, placing them on Xenon.

Yadira Flores 1G
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Re: expanded octet XeF4

Postby Yadira Flores 1G » Sun May 13, 2018 3:17 pm

Expanded octet can only be used depending on the element's place on the periodic table, only if the element is after the 2nd row. F is on the second row, therefore cannot have an expanded octet.

Madeleine Farrington 1B
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Re: expanded octet XeF4

Postby Madeleine Farrington 1B » Sun May 13, 2018 9:49 pm

I understand that for this example, the additional electrons go around Xe because Xe has a d-orbital, enabling an expanded octet, whereas F does not, but in a case where more than one atom in a molecule had a d-orbital, how would you know which atom to draw those extra electrons around?

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Re: expanded octet XeF4

Postby Chem_Mod » Sun May 13, 2018 10:14 pm

You have to use formal charge. You have to minimize the formal charge as much as you can.


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