This entry presents 5-Amino-1,2-dihydro-3H-1,2,4-triazol-3-one (C2H4N4O; CAS 1003-35-6; PubChem CID 135481969) as a 3D-printable ball-and-stick model in which every atom carries its engraved element symbol (C, H, N, O), so the model can be read without a colour key. Atomic coordinates come from the PubChem-computed 3D conformer (not an experimental crystal structure); coordinates and connectivity are unchanged.

Project scope and purpose

MolGod is an open educational-science project that publishes engraved ball-and-stick models of individual chemical compounds. Models are generated deterministically from public structure data and released under CC BY-SA 4.0 together with their identifiers and provenance.

Standard molecular STL files encode geometry only; atom identity, conventionally conveyed by colour, is lost in single-material additive manufacturing. In these models the element symbol is a recessed engraving on each atomic sphere, so atom identity is part of the mesh and remains readable in any print material, visually and by touch.

The design objective is to shorten the time learners need to identify the atoms of a molecule, so that instruction can concentrate on connectivity, bond order and three-dimensional geometry, and to reduce teacher preparation to scaling and slicing a ready file. This is a design rationale: the effect on learning outcomes has not yet been formally evaluated.

Project rationale, related peer-reviewed research and the validation plan: molgod.org/engraved-molecular-models.

Structure at a glance

• 11 atoms: 2 C, 4 H, 4 N, 1 O

• 11 bonds: 9 single, 2 double

• One 5-membered ring

• Functional groups: one primary amino group (-NH2) and one pyridine-type ring nitrogen

• No carbon atom is sp3-hybridised

Use in teaching

• Counting task: students tally the engraved symbols (2 C, 4 H, 4 N, 1 O; 11 atoms) and rebuild the formula C2H4N4O from the model alone.

• Functional groups: find the primary amino group (-NH2) and the pyridine-type ring nitrogen on the model and name each one.

File and printing

STL mesh of 140,640 triangles, a closed (watertight) single solid. Coordinates are in ångström and STL stores no unit, so scale the model deliberately in your slicer. Measured bounding box: 4.879 × 4.558 × 3.661 Å; at scale factor 10 (1 Å to 10 mm, file read in millimetres) the print measures about 48.8 × 45.6 × 36.6 mm. SHA-256: 82f749a8154ef0e063910afcaa39f5826cff869ee3a98daf5fccaa1fc38abcec.

Validation

• InChIKey identical to the PubChem record (PubChem FTP SDF, file dated 2026-10-08): XOHBRLLZSIGHDE-UHFFFAOYSA-N

• Molecular formula identical to PubChem

• Mesh: triangle count in the header equals the actual count; 0 edges not shared by exactly two triangles; 1 connected solid; SHA-256 equal to the published file

Source, licence and identifiers

Full record: molgod.org/molecule/1003-35-6 · Licence and provenance record: molgod.org/licenses/stl/1003-35-6 · Same file on Wikimedia Commons: File:5-Amino-1,2-dihydro-3H-1,2,4-triazol-3-one-3D-molecular-model-engraved-CAS-1003-35-6.stl

• MolGod ID: MG_667-657-426-26

• Wikidata: Q82044002

• IUPAC name: 3-amino-1,4-dihydro-1,2,4-triazol-5-one

• InChIKey: XOHBRLLZSIGHDE-UHFFFAOYSA-N

• SMILES: C1(=NNC(=O)N1)N

• Molar mass 100.08 g/mol (exact mass 100.03851076)

Licence: CC BY-SA 4.0 (licence text). Required attribution: "5-Amino-1,2-dihydro-3H-1,2,4-triazol-3-one 3D model by MolGod.org — https://molgod.org/molecule/1003-35-6/ — CC BY-SA 4.0".