[aloha29293]

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?

[Borek]

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?

[aloha29293]

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...

[Enthalpy]

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