[Kosmonaut89]

Hi! My name is Kosmonaut, I study at Uppsala University, Sweden. I've a question I've been pondering about for some time now.

How can hydrogen fluoride, HF, be a stronger acid than water even though fluorine is a more electronegative element than oxygen?

Relative electronegativities: C < N < O < F
Relative acidities: CH4 < NH3 < H20 < HF
Relative stabilities: -CH3 < -NH2 < HO- < F-

A strong acid gives away a proton easily, how then, can hydrogen fluorine be a better acid than water when fluorine is more electronegative? Doesn't higher electronegativity mean that it attracts hydrogen and therefore donates a proton poorly?

Source:Essential Organic Chemistry 2nd Ed., Paula Yurkanis Bruice

[JustinCh3m]

F is the most electronegative element, and thus it's best at attracting electrons towards itself.  This means that it's "good" at "taking" the electron from hydrogen to produce F- (you're data shows you that F- is very stable).  What's left is H+ (a proton), and this in solution produces the acidity

[Kosmonaut89]

F is the most electronegative element, and thus it's best at attracting electrons towards itself.  This means that it's "good" at "taking" the electron from hydrogen to produce F- (you're data shows you that F- is very stable).  What's left is H+ (a proton), and this in solution produces the acidity

So F- is more stable than O- and therefore F- can get rid of a proton more readily. Just sounds abit counterintuitive but I guess the acidity of atoms' is more dependent on 'stability' rather than electronegativity. Thanks for clearing that up though!