Tangible symmetry elements and space-group models to guide from molecular to solid-state composition

Abstract

The ability to imagine symmetry and the spatial arrangement of atoms and molecules is crucial in chemistry in general. Teaching and understanding crystallography and the composition of the solid state therefore require understanding of symmetry elements and their relationships. To foster the student's spatial imagination, models representing a range of concepts from individual rotation axes to complete space groups have been designed and built. These models are robust and large enough to be presented and operated in a lecture hall, and they enable students to translate conventional 2D notations into 3D objects and vice versa. Tackling them hands-on means understanding them.

Reusing Waste Plastic Caps to Build Inexpensive and Easily Changeable Crystal Structure Models

“…Inexpensive and readily accessible materials are advantages of the cap-and-stick model. The most commonly used materials in previous 3D crystal structure models are tailored or processed spheres, ,,,,, which are closer to the shape of real atoms but require higher cost and/or additional processing that restrict the application and promotion. The used plastic caps are one of the best choices to represent atoms/ions/interstices given the low cost, and easy accessibility and processing.…”

“…Visualizing the properties of a crystal with 3D structural features is a conventional approach to studying crystal structures. − Examples used for such a purpose typically include 2D illustrations in textbooks, 3D object-based models, − and 3D structures animated by computer software. , The multiple developed 3D object-based models ideally characterize the crystal structure features, such as lattice structure, − unit cell, ,,− coordination number, ,,, site occupation, etc. and are commonly employed for visualizing and teaching crystal structures in the classroom.…”

“…and are commonly employed for visualizing and teaching crystal structures in the classroom. However, the reported 3D object-based models require either professional materials or manual dexterity in construction, − ,− which limits the widespread use and students’ participation in the modeling activity. Plastic caps, a kind of ubiquitous waste with various colors and dimensions, are promising materials for building 3D models in chemistry; however, the reported processes used to combine and fix the caps to build molecular models are too complex and time-consuming. , Another challenge in building crystal models is the easy transformation from one structure to another, which will significantly improve the utilization value of materials.…”

Bis(benzoxazol-2-yl)methanides in main group organometallic syntheses and enquiry-based education

“…Instead, pictures and videos were taken to make best possible use of the models in different online teaching approaches. Furthermore, the developed models and the associated teaching approach were transported into the crystallographic community by a publication [223] and conference contribution. [224] Because the physical nature of the space group models restricts them to one unit cell or at least a very small number of unit cells, one crucial aspect of solid-state structure is not addressed at all: periodicity.…”

“…The object files needed to print the parts for a model as shown in Figure 2-23 were made publicly available as part of the respective publication. [223] If a resin printer is available, it can be more straightforward to print the whole model in one piece.…”