Molecular Models and 3D Printing
Three ways to model the geometry of a molecule of water (H2O).
Students are challenged to use computer-aided design (CAD) software to create “complete” 3D-printed molecule models that take into consideration bond angles and lone-pair positioning. To begin, they explore two interactive digital simulations: “build a molecule” and “molecule shapes.” This aids them in comparing and contrasting existing molecular modeling approaches—ball-and-stick, space-filling, and valence shell electron pair repulsion (VSEPR)—so as to understand their benefits and limitations. In order to complete a worksheet that requires them to draw Lewis dot structures, they determine the characteristics and geometries (valence electrons, polar bonds, shape type, bond angles and overall polarity) of 12 molecules. They also use molecular model kits. These explorations and exercises prepare them to design and 3D print their own models to most accurately depict molecules. Pre/Post quizzes, a step-by-step Blender 3D software tutorial handout and a worksheet are provided.
Being able to visualize molecules helps chemistry students (and chemical engineers) analyze the distribution pattern of atoms around a central atom and study its bond types. But the traditional molecular ball-and-stick models typically used for this purpose have limitations—they do not account for lone-pair electrons and the hole positions around the central atom are pre-set to accommodate bonding. As a result, students have difficulty merging the use of the VSEPR theory with molecular models. To overcome these limitations, this activity employs CAD software and 3D printers to enable students to create their own more complete molecule representations. Once students understand the significance of accurately evaluating molecular models and their features—characteristics such as bond angle, lone-pair electrons—and how those features dictate molecular geometry, they can take advantage of 3D technology to better predict chemical and physical properties.
This skillset has significant real-world chemical engineering applications for influencing molecular geometry to create chemical compounds such as polymers, paper, dyes, drugs, plastics, fertilizers, foods and petrochemicals that are custom designed for clients and consumers. The development of these end products requires a solid understanding of molecular structure and can ultimately affect our health, environment and cost of living. With the use of 3D printers, chemical engineers can begin to further enhance product quality by developing prototypes that add functionality to complement specific chemical reactions.
After this activity, students should be able to:
- Draw Lewis dot diagrams for various examples of covalent molecules and polyatomic ions.
- Create models of molecules/ions, including their molecular structures and geometries, using CAD software and 3D printers.
- Apply the VSEPR theory to predict molecular geometry and polarity.