Intermediate Topic 216 of 1102 Bonding & Molecular Structure
Van der Waals Radius
Half the closest distance between nonbonded atoms of neighbouring molecules.
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In-depth explanation of Van der Waals Radius
The van der Waals radius of an atom is half the closest distance of approach between two nonbonded atoms of neighbouring molecules. It describes the effective size of an atom in contacts that do not involve chemical bonding. Van der Waals radii are always larger than covalent radii, because nonbonded contacts are set by the outer extent of the electron cloud rather than by a bond. The radius controls packing in molecular crystals and steric hindrance in organic molecules. Values are derived from crystallographic data and tabulated for most elements.
Going deeper: Van der Waals Radius
Key ideas: Use it to decide contact distances: the sum of two van der Waals radii equals the nonbonded distance. Typical values in pm: H 120, C 170, N 155, O 152, F 147, Cl 175. Atoms closer than the sum indicate a special interaction, like hydrogen bonding or halogen bonding. Used in molecular modelling (space-filling models) and steric clash checks.
Common mistakes and connections: Students mix up this value with the covalent radius or with the ionic radius, or say van der Waals radii are always about double covalent ones. Another error is expecting atoms to be hard spheres, whereas the radius depends on the direction and chosen density cutoff. Links to London forces, packing, steric effects and protein structure.
Visualization of Van der Waals Radius
Van der Waals radii show how closely nonbonded atoms approach; they are always larger than the covalent radii of the same atoms. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Carbon has a van der Waals radius of about 170 pm, compared with a covalent radius of about 77 pm.
Frequently asked questions about Van der Waals Radius
What is Van der Waals Radius?
Half the closest distance between nonbonded atoms of neighbouring molecules.
Is Van der Waals Radius a beginner, intermediate or advanced topic?
Van der Waals Radius is a intermediate topic in Bonding & Molecular Structure. It builds on the vocabulary of beginner topics in this area.
What should I learn before Van der Waals Radius?
Study these earlier topics in Bonding & Molecular Structure first: Hypervalency, Three-Center Two-Electron Bond, Banana Bonds.
What comes after Van der Waals Radius?
The next topics in Bonding & Molecular Structure are Covalent Radius and Electron-Pair Repulsion Ranking.
Can I practise Van der Waals Radius with quizzes?
Yes. The interactive lesson includes a self-check question on Van der Waals Radius, and the Bonding & Molecular Structure quiz draws on every topic in this area.
Where Van der Waals Radius fits in Bonding & Molecular Structure
Van der Waals Radius is topic 101 of 104 in Bonding & Molecular Structure.