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Radius Ratio Rule (2D): Ionic Coordination Geometry

Interactive 2D 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 a draggable projected view and live anion-anion overlap detection.

Chemistry & Materials2DModerate60 FPS📱 Mobile-adapted⇄ 3D version

Details

CategoryChemistry & Materials

RenderingCanvas 2D

DifficultyModerate

Target FPS60

ControlsDrag the cation (r+) and anion (r-) radius sliders, force a coordination number from the dropdown or leave it on Auto, toggle auto-rotate, jump to a real-ion preset (NaCl, CsCl, ZnS, TiO2), drag the canvas to orbit the projection and scroll or pinch to zoom.

inorganic chemistryionic bondingcrystal structurePauling rulecoordination numberchemistry

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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 2D canvas projection of the same coordination polyhedron used by the 3D version 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. Drag the view to rotate the projection and scroll to zoom; 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 circles visibly collide.

⚙ Under the hood

Drag cation and anion radii on a rotatable 2D projection of a real coordination polyhedron and watch Pauling's radius-ratio rule predict linear, trigonal, tetrahedral, octahedral, cubic or cuboctahedral packing, with live anion-anion overlap detection, drag-to-rotate and scroll-to-zoom.

inorganic chemistryionic bondingcrystal structurePauling rulecoordination numberchemistry

2D · HTML5 Canvas 2D · 60 FPS target · runs fully client-side, no install