Glossary
ionic bond
An ionic bond is the attraction between two oppositely charged ions, formed when one atom gives electrons to another — a metal and a nonmetal, usually.
An ionic bond is the attraction between two ions of opposite charge, and the ions exist because one atom gave electrons away and another took them. It forms between a metal, which holds its outer electrons loosely, and a nonmetal, which needs electrons to complete its shell: sodium hands its one valence electron to chlorine, and Na+ and Cl- then stick together by charge alone. The result is not a molecule but a lattice — each ion surrounded by ions of the opposite charge in a repeating pattern, which is why table salt is a crystal and not a gas. That structure explains the properties a question asks about. Ionic compounds melt at high temperature because separating the lattice takes a lot of energy, they shatter rather than bend because a shift puts like charges side by side, and they conduct electricity when melted or dissolved because the ions are then free to move.
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Related terms
- ion — An ion is an atom or group of atoms with a charge, made by losing electrons (positive cation) or gaining them (negative anion).
- covalent bond — A covalent bond is a shared pair of electrons between two atoms, the usual bond between nonmetals and the bond that holds molecules together.
- valence electron — A valence electron sits in an atom's outermost occupied shell, and the count there decides which bonds the atom forms and what charge its ion carries.
- oxidation — Oxidation is the loss of electrons by a species; it always comes with a reduction, in which another species gains them.
Source: NIST periodic table and reference data for the atomic masses and half-life figures, NIH PubChem for the substance data, and NIST Special Publication 811 for the unit conventions — the same sources the chemistry guide cites. All three are US federal government material, not subject to copyright in the United States. Every definition, example and calculation above was written for this course; no dictionary or textbook text is reproduced. (NIST and PubChem accessed 2026-10-26; definitions written 2026-10-27)