Question

Why are hydrogen bonds able to form between water molecules?

Answer 1

It all comes down to electronegativity and polarity.

Explanation:

Hydrogen bonding is an attractive force between two molecules that relies on the slight polarity of the O-H, O-F, or O-N bond. Due to the electronegativity difference between the atom pairs mentioned, electrons are unevenly shared across the covalent bond.

The electronegativity difference for each bond is as follows:
`O-H`: `DeltaEN=abs(3.44-2.20)=1.24`
`O-N`: `DeltaEN=abs(3.44-3.04)=0.40`
`O-F`: `DeltaEN=abs(3.44-3.98)=0.54`

The image above depicts water molecules. Notice how there is a slight positive charge `delta^+` near the hydrogens and a slight negative charge `delta^-` near the oxygen. The `delta^+` of the hydrogens can interact with the `delta^-` of the oxygens on other water molecules (as depicted by the dashed lines)

Hydrogen bonding is the strongest type of intermolecular force. Substances that exhibit hydrogen bonding tend to have relatively high boiling points and melting points.