Hydrogen bonds
The bridges or hydrogen bonds are a type of dipole-dipole forces which occur when hydrogen binds a molecule with a very small atom size electronegative, such as nitrogen, oxygen and fluorine.
These intermolecular interactions are weak but stronger than normal dipole-dipole interactions. This implies that substances that have hydrogen bonds have higher melting and boiling points than expected. For this reason, the water at room temperature is a liquid and not a gas such as H2S.
As we have seen, dipoles are produced when the area of the most electronegative atom has a negative partial charge, as it has a greater tendency to capture electrons, while in the area of the least electronegative atom, the partial charge will be positive.
The hydrogen bonds may be established between different molecules, as is the case of the water, or between different regions within the same molecule, as in the case of proteins or nucleic acids, to be partially responsible for the secondary structure, tertiary structure and quaternary structure of proteins and nucleic acids.