# Why is the fluorine atom a poor hydrogen bond acceptor?

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1. Apr 29, 2015

### sgstudent

My notes states that fluorine is too highly electronegative and hence clings on too tightly to its lone pair of electrons and so it cannot accept hydrogen bonds as well. However, it also stated that a hydrogen bond will be stronger if the electron density on the electron rich atom the stronger the hydrogen bond. These 2 statements seem to contradict though.

I read online from this link http://www.quora.com/Why-can-chlorine-atoms-not-form-hydrogen-bonds-even-though-they-have-very-similar-electronegativity-to-nitrogen-which-can [Broken] that a hydrogen bond has an electrostatic component, but what differentiates it from a dipole-dipole interaction is that it also has a covalent component. And since the F clings onto its electrons too tightly it would not want to form a covalent bond which is why its a poor HBA and forms weak hydrogen bonds.

So is the second statement wrong?

Last edited by a moderator: May 7, 2017
2. Apr 30, 2015

### DrDu

I wouldn't sign that. The hydrogen bond in the ion FHF$^-$ is one of the strongest known.

3. Apr 30, 2015

### SteamKing

Staff Emeritus
It's not clear what this statement means: "fluorine is too highly electronegative and hence clings on too tightly to its lone pair of electrons and so it cannot accept hydrogen bonds as well."

Fluorine, atomic number 9, has 7 electrons in its valence shell, hence it is lacking 1 electron to have a full complement, which is why it is grouped with the halogens in the Periodic Table.

4. Apr 30, 2015

### DrDu

And how does this contradict the fact that fluorine, also has lone pairs that participate in hydrogen bonding?
I think it is also amply clear from the context that sgstudent is not talking about a fluorine atom but some fluorine compounds like HF.

5. Apr 30, 2015

### SteamKing

Staff Emeritus
That's funny, because his notes didn't say anything about fluorine compounds, just fluorine.

6. Apr 30, 2015

### DrDu

Even a fluorine atom has 3 lone pairs ...