One at the center, twelve around it — the densest thing space allows. Not stored. Forced. Drag it; the geometry is the address.
One node, bonded to all twelve. The only one that is. It carries no surface, sits at the origin, and is the reference every shell address is measured from. Remove it and the twelve have no center to be a shell of.
Each shell node touches 4 siblings + the center = 5 bonds. None touches all — only the center does. The twelve fall into three mutually perpendicular squares (the x, y, z planes): the shell is three rings, not one ring of twelve.
The 13 and the 1 + 12 are forced — this is the densest sphere packing, coordination number 12, the first closed shell at 13. It is the same for anyone who packs identical spheres in three dimensions; you cannot rename it, fit it, or argue it away. Which node is the anchor, and how the twelve route, is yours to assign. The geometry is given. The addressing is built. Keep those apart and the structure holds under any solvent — because 3D space and your architecture bottomed out at the same shape: a center coordinating a closed shell.