When studying environmental science, one type of atomic bond you need to be familiar with is the hydrogen bond. A hydrogen bond results when some of the atoms in a covalently bonded molecule pull the shared electrons to one side of the molecule, creating an electrical imbalance in the molecule. (Remember that electrons have a negative electric charge.)
When an imbalance of electrical charge occurs within a molecule, the molecule is said to be polar or to exhibit polarity — in which case one end has a positive charge and the other has a negative charge (just like a magnet).
A polar molecule acts a little like an atom in need of an electron. Its positively charged end is attracted to negatively charged things around it — most commonly the negatively charged sides of other polar molecules.
The most common example of hydrogen bonding involves water molecules. This figure illustrates how the covalent bond between oxygen and hydrogen creates an electrical imbalance in water molecules and how, as a result, the negative end of one water molecule is attracted to the positive ends of another water molecule forming hydrogen bonds.
Hydrogen bonds are weak compared to covalent and ionic bonds, but these weak bonds play an important role in the environment and in living things. They’re important in forming DNA chains, and they give liquid water some seemingly magical properties.