Abstract
<jats:p>The modern periodic table, while a foundational framework of chemical science, presents inherent structural limitations: the positional ambiguity of hydrogen, the physical segregation of the f-block elements as a detached appendix, and the inability of a planar representation to simultaneously encode multiple periodic trends in an intuitive spatial manner. This study proposes a novel three-dimensional periodic table modeled on the geometry of a Reuleaux tetrahedron, a geometric solid of constant width formed by the intersection of four spheres of radius S centered at the vertices of a regular tetrahedron. The three curved faces of the tetrahedron serve as designated “zones” for the s, p, and d blocks respectively, while the f-block is accommodated as a minimal-area surface protrusion, the negligible size of which visually communicates the Lanthanoid and Actinoid contractions. Hydrogen’s positional duality between Group 1 (alkali metals) and Group 17 (halogens) is resolved through a topological loop at the apex of the model, simultaneously elucidating salt formation between these groups. Group 14 metalloids are positioned at the central edge to encode the peak of the valency trend across a period. A controlled downward tilt of the structure encodes the empirical decrease in atomic radii across periods while preserving the increasing trend down groups. Atomic radius data from the NCBI PubChem database are employed to validate block and group spatial assignments. The proposed model offers a structurally coherent, scalable, and pedagogically enriched alternative to the conventional two-dimensional periodic table. The curved geometry of the Reuleaux tetrahedron additionally provides a continuous framework for representing inherently non-linear periodic trends, including atomic-radius variation and contraction phenomena</jats:p>