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expanded octet XeF4

Posted: Fri May 11, 2018 10:57 pm
by 804991762_4A
Can someone clarify as to why in XeF4, you cant make a double bond, instead of having 2 lone pairs?

Re: expanded octet XeF4

Posted: Fri May 11, 2018 11:15 pm
by Valeria Viera 1B
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)

Re: expanded octet XeF4

Posted: Fri May 11, 2018 11:17 pm
by Shimran Kumar 1C
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.

Re: expanded octet XeF4

Posted: Sun May 13, 2018 2:34 am
by Steven Luong 1E
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.

Re: expanded octet XeF4

Posted: Sun May 13, 2018 3:11 pm
by Chem_Mod
F cannot have more than 8 electrons. F cannot have an expanded octet

Re: expanded octet XeF4

Posted: Sun May 13, 2018 3:16 pm
by Chris Qiu 1H
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.

Re: expanded octet XeF4

Posted: Sun May 13, 2018 3:17 pm
by Yadira Flores 1G
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.

Re: expanded octet XeF4

Posted: Sun May 13, 2018 9:49 pm
by Madeleine Farrington 1B
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?

Re: expanded octet XeF4

Posted: Sun May 13, 2018 10:14 pm
by Chem_Mod
You have to use formal charge. You have to minimize the formal charge as much as you can.