ACORN Framework Booklet Series The ACORN framework is a geometric curvature–closure approach to fundamental physics in which mass, quantisation, and dynamical behaviour arise from closed circulation of intrinsic curvature channels governed by a compact canonical operator structure. From these canonical relations emerge invariant closure norms, quantised loop actions, and universal recurrence relations organising stable physical structure. The ACORN booklet series develops the consequences of this canonical framework across multiple domains of physics. Each booklet begins from the frozen Canon and explores how familiar physical phenomena arise as projections or consequences of curvature closure dynamics. This booklet develops the atomic sector of the ACORN framework. Within ACORN, atoms are interpreted as composite curvature structures in which proton and neutron closures form a central curvature knot while electron closures organise into stable orbital circulation patterns surrounding the nucleus. These electron configurations correspond to discrete curvature winding states whose stability reflects quantised closure conditions. Electron shells arise from permitted curvature winding modes around the nuclear closure structure. The familiar shell capacities of atomic structure emerge from the combinatorial organisation of these curvature modes, constrained by closure compatibility and topological exclusion between overlapping circulation states. Within this interpretation: • atomic nuclei form composite curvature closures within the Matter Cone,• electrons represent stable minimal closure modes orbiting the nuclear structure,• electron shells correspond to discrete curvature winding levels,• and exclusion principles arise from topological constraints on curvature circulation. ACORN: Atomic Structure therefore proposes that the organisation of atoms and their electron shells reflects geometric winding structure within the curvature–closure framework. This booklet extends the ACORN interpretation of matter from primitive particles and nuclei to the structured organisation of atoms.