Hydrogen Bonding

Hydrogen bonding is the term used to describe a VERY strong dipole-dipole attraction that occurs between molecules that contain hydrogen atoms bonded to fluorine, oxygen or nitrogen atoms.

Before you explore this idea further there are several VERY important things to understand first:

• Hydrogen bonding is NOT bonding. The name is unfortunate and confusing but we're stuck with it.
• Hydrogen bonding does not occur unless the hydrogen atom is attached to the F, O or N atom. In other words, just because a molecule has both O and H, does not mean that there will be hydrogen bonding. 

Understanding hydrogen bonding first requires us to think about hydrogen. Hydrogen atoms, as the simplest type of atom, contain one proton and one electron.

If an electron is pulled away from any atom, a positive charge is left behind, but if the electron is pulled away from a hydrogen atom, it leaves behind a bare proton.

To understand why that matters you can think of this analogy. You walk outside on a cold winter day and someone steals the hat off of your head. If you started with 10 hats, you head will be a little colder. If, on the other had, you started with only one hat, losing that hat would make you cold.

So, any atom that loses an electron will be positive, but a hydrogen that loses an electron will become "pure, perfect positive" - a proton.

This idea holds even if the atom doesn't completely lose the electron - that is, even if the electron is pulled off center as in a polar bond. But, how extreme that is depends on the nature of that polar bond.


When a hydrogen atom is involved in a polar covalent bond, the "positive side" of that bond is more positive than it would be with a different atom. When the hydrogen  atom is bonded to an extremely electronegative atom (F, O, N) the hydrogen becomes almost as positive as a +1 ion.

That means that the attraction between one molecule of HF and another HF is almost as strong as an ion-ion attraction. That is a hydrogen bond.

In the diagram, here, The yellow highlighting shows the "warped" bond focused on the fluorine and nearly "abandoning" the hydrogen atom.

So, the molecules shown below DO exhibit hydrogen bonding with themselves and with each other,

While the molecules here do NOT exhibit hydrogen bonding even though they contain H atoms and O, or F atoms (although they do exert dipole-dipole attractions).