This study investigates the stereochemistry and electronic structure of two compounds, XeO3E and SeOF2E, both conforming to the general formula MX3E (M = Xe6+, Se4+) and featuring ns2 lone pairs (E). These orthorhombic crystals were selected to analyze the steric role of ME and the influence of lone pairs on Fluorine and Oxygen atoms. Detailed stereochemical analyses were performed using density functional theory (DFT) combined with two- and three-dimensional Electron Localization Function (ELF) mappings. The resulting metrics indicate that the ns2 radii of Xe (0.88 Å) and Se (0.85 Å) are comparable to first-period atoms, highlighting the crucial steric effect of these lone pairs on molecular shape and crystal packing. Fluorine lone pairs form electronic tori aligned along the M − F bonds, whereas oxygen lone pairs appear as twin maxima with versatile opening angles ranging from ∼100° to ∼160°, allowing flexible network adjustments. Site-projected density of states (DOS) confirm that both compounds are insulating, with energy gaps reflecting the separation between bonding and nonbonding valence states, the latter being responsible for lone pair development and their influence on the crystal structure.


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