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workbook Quiz 2 preparation #7

Posted: Sat Oct 22, 2016 7:29 pm
by 904779609
Why does the central Xenon atom have the extra pair of electrons added to its lewis structure?

Re: workbook Quiz 2 preparation #7

Posted: Sun Oct 23, 2016 12:38 pm
by Chem_Mod
Are you sure the other oxygen does not also have the double bond? Otherwise the molecule would have formal charge.

Re: workbook Quiz 2 preparation #7

Posted: Mon Oct 24, 2016 11:37 pm
by Christian_Makar_2D
That extra pair of electrons on Xenon is there because when you count the electrons you end up with only 32, but you need 34 total. So since Xenon is an exception to the octet rule, it can hold more electrons and that one lone pair is added to it.

Re: workbook Quiz 2 preparation #7

Posted: Mon Oct 24, 2016 11:50 pm
by Armo_Derbarsegian_3K
The other oxygen should form a double bond as well. So you get Xe with a lone pair, both Fs single bonded with 3 lone pairs, and the 2 Os double bonded with 2 lone pairs.

:O:
.. || ..
:F - Xe - F:
.. || ..
:O:

This Lewis structure will give each atom a formal charge of 0 and will be the biggest contributor to the resonance hybrid. What you did is also correct and is one of the resonance structures for XeO2F2, but similar to the SO2 example from the course reader, this resonance is better due to formal charges.