The simulator displays seven molecules whose shapes follow valence shell electron-pair repulsion (VSEPR). Switch molecules, reveal or hide lone-pair domains and read the domain counts and angle for each, in a 3D scene you can rotate.
• A central atom, bonded outer atoms, lone-pair domains and a bond-angle arc. • A molecule selector: CO₂ linear, BF₃ trigonal planar, CH₄ tetrahedral, NH₃ trigonal pyramidal, H₂O bent, PCl₅ trigonal bipyramidal and SF₆ octahedral. • Toggles for lone-pair domains, a slow orientation tour and explanatory particles. • Readouts: bonding domains, lone-pair domains, total domains and the representative bond angle. Experiments: water with lone pairs (four domains, two bonded atoms, bent) and six-coordinate SF₆ (octahedron).
Steric number equals bonding domains plus lone pairs, and domains spread out to minimize repulsion. Double and triple bonds each count as one domain. Preset angles are CO₂ 180°, BF₃ 120°, CH₄ 109.47°, NH₃ about 107°, H₂O 104.5°, PCl₅ 90°/120°/180° and SF₆ 90°/180°.
Geometries are presets and bond lengths are illustrative. VSEPR is a qualitative rule, not an energy minimization calculation, so small angle differences are quoted values rather than computed ones.
Oxygen has four electron domains, two bonding and two lone pairs. The domains point toward tetrahedral positions, so the two atoms form a bent shape near 104.5°.
Lone pairs take more room than bonding pairs, compressing the bond angles. That is why NH₃ (about 107°) and H₂O (104.5°) are smaller than the tetrahedral 109.47°.
Each double or triple bond counts as one domain, as in CO₂, where two double bonds give two domains and a linear 180° shape.
PCl₅ has five (trigonal bipyramidal, with 90°, 120° and 180° angles) and SF₆ has six (octahedral, with 90° and 180°).