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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: aloha29293 on April 02, 2018, 04:49:55 PM

Title: Electronegativity
Post by: aloha29293 on April 02, 2018, 04:49:55 PM

Hello,

I would like to know why O is more electronegative than S? I ask because since S has a bigger atom, the electron would be better delocalized, hence leading to a better acidity (although text books state that electronegativity is the main criterion for, for example, the rejection of H from OH...). Isn't it therefore better that the atomic radius is the main criterion on which the I-effect or the acidity of a molecule shoud be based on?

Title: Re: Electronegativity
Post by: Borek on April 02, 2018, 05:00:00 PM

Quote from: aloha29293 on April 02, 2018, 04:49:55 PM

I would like to know why O is more electronegative than S?

Because when you use experimental data to calculate it according to the definition, you get a higher number for O than for S?

Title: Re: Electronegativity
Post by: aloha29293 on April 02, 2018, 05:12:11 PM

Yes, of course, but why is SH, for example, more acid than OH, although "electronegativity" would be the main criterion?
It is because of the bigger atomic radius, not of the EN; otherwise it would mean that O in OH is more likely to repel from H than in SH...

Title: Re: Electronegativity
Post by: Enthalpy on April 03, 2018, 11:48:33 AM

Electronegativity doesn't relate directly with acidity.
Electronegativity would decide a reaction like
H+SH  ::equil:: H⁺+HS^-
but the reaction that tells acidity is rather
H₂S ::equil:: H⁺ + HS^-
where the hydrogen is already bonded.