Bunch

tie the balloons on; they find the shape themselves.

each electron pair round an atom is a balloon tied at one knot; drag bond pairs and lone pairs up from the chalk ledge, watch the bunch settle into its VSEPR shape, and move lone pairs to where they rub least

Electron pairs round a central atom push apart like balloons tied at one knot. Count them: bond pairs plus lone pairs gives the steric number, which fixes the arrangement and the hybridisation (4 sp3 tetrahedral, 5 sp3d trigonal bipyramidal, 6 sp3d2 octahedral). The shape is what you see with the lone pairs hidden: NH3 pyramidal (107°), H2O bent (104.5°). Lone pairs take more room, so with five pairs they sit in the middle ring, where only two neighbours are at 90° instead of three: SF4 is a see-saw, ClF3 a T. With six, two lone pairs sit opposite each other: XeF4 is square planar.

Concepts: chemistry, atomic-structure, symmetry.

An interactive you play with one thumb, on Wundr.