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Radius Ratio Rule: Ionic Coordination Geometry

Interactive 3D radius-ratio simulator: drag cation and anion radii and watch Pauling's rule predict whether an ionic crystal packs into linear, trigonal, tetrahedral, octahedral, cubic or cuboctahedral coordination — with live overlap detection showing exactly why each geometry breaks down.

Chemistry & Materials3DModerate60 FPS📱 Mobile-adapted

Inorganic chemistry's most direct link between an ion's raw size and the crystal structure it forms is Pauling's radius-ratio rule. This simulator builds a real 3D coordination polyhedron — a central cation surrounded by touching anions — and lets you drag the cation and anion radii independently, watching the predicted coordination number and packing geometry switch between linear, trigonal planar, tetrahedral, octahedral, cubic and cuboctahedral exactly where the geometry demands it. Overriding the auto-picked coordination number shows why the rule exists in the first place: forcing too many anions around a cation that is too small makes the anion spheres visibly collide.

⚙ Under the hood

Drag cation and anion radii on a real 3D coordination polyhedron and watch Pauling's radius-ratio rule predict linear, trigonal, tetrahedral, octahedral, cubic or cuboctahedral packing, with live anion-anion overlap detection.

inorganic chemistryionic bondingcrystal structurePauling rulecoordination numberchemistry

3D · Three.js / WebGL renderer · 60 FPS target · runs fully client-side, no install