Chapter 51: Molecular Geometry

Molecular geometry—the three-dimensional arrangement of atoms in a molecule—determines virtually every macroscopic property: melting point, solubility, reactivity, colour, biological function. The Valence Shell Electron Pair Repulsion (VSEPR) model predicts geometry from a single principle: electron pairs around a central atom arrange themselves to minimise mutual repulsion. In Category τ, VSEPR acquires a structural foundation: electron pairs are τ² modes on the fiber T², and repulsion is the Pauli–Coulomb exclusion forcing these modes to maximal angular separation. This chapter develops the VSEPR framework, catalogues the common molecular geometries, treats lone-pair distortions, derives molecular polarity from spatial symmetry, and connects geometry to biological function.