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Chlorine in center: electronegativity vs. formal charge

Posted: Mon Nov 04, 2019 9:58 am
by Anisha Chandra 1K
What if the central atom is the most electronegative atom? (Ex. chlorine in the center in ClO4-) Would you want chlorine to be 0 or more negative than the oxygens since chlorine is more electronegative?

What would the correct structure be for Cl04-? I've seen two different answers - one with 3 double bonds with oxygens and one single, placing negative FC on oxygen but also one with 4 double blonds, placing negative FC on central chlorine atom

Re: Chlorine in center: electronegativity vs. formal charge

Posted: Mon Nov 04, 2019 11:56 am
by Brian_Ho_2B
Anisha Chandra 4H wrote:What if the central atom is the most electronegative atom? (Ex. chlorine in the center in ClO4-) Would you want chlorine to be 0 or more negative than the oxygens since chlorine is more electronegative?

What would the correct structure be for Cl04-? I've seen two different answers - one with 3 double bonds with oxygens and one single, placing negative FC on oxygen but also one with 4 double blonds, placing negative FC on central chlorine atom

You want the central atom to have zero formal charge and if there's any negative formal charges, you want to delocalize them to the atoms surrounding the center atom. The structure of ClO4- with the 3 double bonds and 1 single bond on Cl with negative FC on the oxygen atoms is more stable because the center atom's FC is zero and the negative charge is delocalized.

Re: Chlorine in center: electronegativity vs. formal charge

Posted: Thu Nov 07, 2019 11:22 am
by VPatankar_2L
Also since Oxygen is more electronegative that Chlorine, it can carry the -1 charge.

Re: Chlorine in center: electronegativity vs. formal charge

Posted: Fri Nov 08, 2019 10:00 am
by Angela Patel 2J
VPatankar_3L wrote:Also since Oxygen is more electronegative that Chlorine, it can carry the -1 charge.

Is oxygen more electronegative than chlorine? I thought it was the other way around?

Re: Chlorine in center: electronegativity vs. formal charge

Posted: Sun Nov 10, 2019 10:29 am
by VPatankar_2L
I think it has to do with the fact that Chlorine's atomic radius is larger than that of Oxygen, so Oxygen's outermost electrons are held more tightly to the nucleus than Chlorine's outermost electrons. Also, the change in electronegativity is greater as you move up or down a group, than if you move across a period.