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Molecules have characteristic shapes that are important for their functions.

Any diatomic molecule, such as molecular oxygen or hydrogen, is always linear.

As the number of atoms increases, the arrangement of electrons around the central atom influences the shape of the molecule, allowing it to bend and form more complex structures.

Negatively charged electron groups repel one another and try to stay as far apart as possible.

For example, in a water molecule, the oxygen atom forms two bonding pairs of electrons with two hydrogen atoms and has two additional pairs of electrons that are not involved in bonding, called lone pairs of electrons.

These two lone pairs push the bonding pairs around the oxygen atom to about 104.5 degrees, where repulsion is lowest, giving the water molecule a bent shape.

Some biological molecules, such as DNA and proteins, may contain anywhere from a few to millions of atoms.

These large biomolecules are stabilized by intermolecular forces, such as hydrogen bonding, or intramolecular forces, like hydrophobic interactions, allowing them to form long chains and rings that fold into three-dimensional shapes.

They also use structure-specific recognition to interact with other molecules.

For example, opiates with active regions that are structurally similar to endorphins can bind to endorphin receptors and relieve pain.