27 Jun 2016

Solid State Stoichiometry Online

Web Resources and Apps

Submitted by George Lisensky, Beloit College
Categories
Description: 

The page has JSmol structures for unic cells including cubic, body centered cubic, and face centered cubic unit cells as well as for CsCl, Ni3Al, Cu2O, NaCl, CaF2, ZnS, diamond, Li3Bi, NaTl, NiAl and ReO3The advanced page also has triclinic, monoclinic, hexagonal, orthorhombic, and tetragonal cells with all possible centering.

The purpose of this site is to help students visualize how much of an atom is in the unit cell so that compound stoichiometry can be determined. 

 

 
Learning Goals: 

Students can determine the empirical formula from an extended solid state structure.

Students will be able to understand that a unit cell represents the contents of an extended solid.

Implementation Notes: 

We have used a physical model kit to build solid state structures in class for many years. After building a few structures, students often want to try some more structures. These online models were created to allow continued study and practice out of class.

Cubic unit cells are appropriate for an introductory course. The advanced unit cells include all crystal systems and centering options.

The display options "faces" and "perspective" are recommended for counting atoms within the cell. 

Time Required: 
1 hour
Evaluation
Evaluation Methods: 

We provide a built solid state 3D physical model that the students had not previously seen as a quiz question where students are asked to show their work in calculating the stoichiometry

See the evaluation questions file and activity answer key in the companion Solid State Stoichiometry Activity learning object.

Evaluation Results: 

Most students have been able to determine the empirical formula for any of these structures. They sometimes struggle with the difference between a corner, an edge, a face, and inside the unit cell. Students are generally able to determine the stoichiometry for an extended solid that they have not previously seen.

Creative Commons License: 
Creative Commons Licence

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