Waals

Waals, often written van der Waals, is a Dutch surname and toponym. The name derives from the Dutch for “from the Waal,” referring to the Waal river valley in the central Netherlands. As a surname it occurs in the Netherlands and Dutch-speaking communities, and the form van der Waals is widely used in scientific literature to honor the physicist Johannes Diderik van der Waals.

Johannes Diderik van der Waals (1837–1923) was a Dutch theoretical physicist whose work on the behavior of real gases and molecular interactions laid important foundations for physical chemistry and condensed matter physics. Several concepts bear his name, including van der Waals forces—weak, noncovalent attractions between molecules arising from transient dipoles; the van der Waals equation of state—a modification of the ideal gas law that accounts for molecular size and intermolecular attractions; and the van der Waals radius—an effective atomic size used in modeling how atoms and molecules approach each other.

In modern science, the van der Waals framework informs a wide range of disciplines, from liquids and biomolecules to materials science. van der Waals forces explain adhesion, condensation, and molecular packing, while van der Waals heterostructures describe layered assemblies of two-dimensional materials held together by these forces. The name continues to appear in research and discussions of intermolecular interactions, real-gas behavior, and nanoscale materials.