## Chlorine in center: electronegativity vs. formal charge

$FC=V-(L+\frac{S}{2})$

Anisha Chandra 1K
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### Chlorine in center: electronegativity vs. formal charge

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

Brian_Ho_2B
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Joined: Fri Aug 09, 2019 12:16 am

### Re: Chlorine in center: electronegativity vs. formal charge

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.

VPatankar_2L
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### Re: Chlorine in center: electronegativity vs. formal charge

Also since Oxygen is more electronegative that Chlorine, it can carry the -1 charge.

Angela Patel 2J
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Joined: Sat Aug 24, 2019 12:17 am

### Re: Chlorine in center: electronegativity vs. formal charge

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?

VPatankar_2L
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### Re: Chlorine in center: electronegativity vs. formal charge

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.

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