EOSH-Closure: An Oxidation-State-Anchored Electron-Counting Framework for Main-Group Structure Prediction

We present EOSH-Closure (Electron Ownership via Shell Hierarchy), a parameterfree, arithmetic electron-counting framework that predicts AX m E n molecular geometry from a binary formula and total charge alone. The method applies a single operationclosure-core subtraction-to the IUPAC ionic-limit electron count e i = Z i −O i , yielding an integer valence descriptor n val (i) from which lone pairs, steric number, and geometry follow without free parameters or Lewis-structure drawing. Validated against 23 binary fluorides (interhalogen, noble-gas, and hypervalent p-block; steric numbers 2-7) and a further 15 non-fluoride compounds (Cl, Br, O, S, N ligands; Table S4 †), the framework recovers all 38 experimentally established geometries correctly (38/38). Three supplementary descriptors-the Closure Nuclear Charge Ratio η (D8), the Closure Compatibility Index Γ (D9), and the LCP minimum central-atom radius r ion,min (D10)-extend the electronic gate to a three-gate hierarchy (electronic, compatibility, steric) that correctly predicts the existence of [SiF 6 ] 2and the non-existence of [SiCl 6 ] 2from first principles. A systematic 5 733-entry AB m atlas maps electronic admissibility across seven ligand families, and a four-level routing protocol identifies when VSEPR localisation fails and higher-level theory is required. The linear combination δ(i) = λ • OS(i) + (1 − λ) • FC(i) unifies formal charge and oxidation state on a single ionicity continuum; six prospective computational tasks define explicit falsification criteria connecting the framework to ab initio electronic structure.