What is a link between atoms in a molecule called?

The link between atoms in a molecule is called a chemical bond. Chemical bonds arise from electrical attractions involving the atoms' nuclei and electrons, and they give molecules their structure and stability.

The most familiar bond types are covalent, ionic, and metallic. In a covalent bond, atoms share electrons; the hydrogen atoms in H₂ provide a simple example. In an ionic bond, electrons are transferred to produce oppositely charged ions, as in sodium chloride. Metallic bonding involves atoms sharing mobile electrons throughout a metal lattice. Real bonds can show mixed character rather than fitting perfectly into only one category.

Bonding is not the same as an intermolecular force. A covalent O–H bond holds atoms together inside a water molecule, while hydrogen bonds help attract separate water molecules to one another. Bond strength and arrangement influence melting points, boiling points, hardness, conductivity, and chemical reactivity. Chemists often draw bonds as lines in structural formulas, but those lines represent a model of electron distribution rather than a physical rod connecting the atoms.