What is a foundations inorganic course? Here is a great description
I typically evaluate this activity through class participation although the answer key is posted after class to let the students evaluate their own understanding of concepts. The students do know that they will be tested on the material within the activity and usually I have a density problem on the exam.
This activity is designed to give the students more freedom as they move from the first density calculation to the last set of calculations. Within the last set of calculations, they encounter a hexagonal unit cell so that may require some additional intervention to get them to think about how to calculate the volume of a hexagonal unit cell.
This activity is designed to relate solid-state structures to the density of materials and then provide a real world example where density is used to design a new method to explore nanotoxicity in human health. Students can learn how to calculate the density of different materials (gold, cerium oxide, and zinc oxide) using basic principles of solid state chemistry and then compare it to the centrifugation method that was developed to evaluate nanoparticle dose rate and agglomeration in solution.
A student should be able to calculate a unit cell volume from structural information, determine the mass of one unit cell, and combine these two parameters to calculate the density for both cubic and hexagonal structures. In addition, students will have an opportunity to read a scientific article and summarize the major findings, place data in a table, and explain the similarities and differences between the densities calculated in the activity and the experimental values that are reported in the literature.
I have used this activity in our first semester inorganic chemistry course when we cover solid-state materials. One thing to note is that I do use 2-D projections to describe structures and we cover that in a previous activity. You could remove 2-D projections from this activity if it is not something that you previously covered.
Evaluation methods could include grading as an in-class worksheet, trading with a partner for peer grading or turned in as an out-of-class graded homework assignment.
Currently, this activity has not been tested in a classroom. Please post how your students did!
This in-class activity is designed to assist students with the visualization of solid-state close-packed structures, using metal-sulfide nanocrystalline materials as a an example system. Students will be asked to visualize and describe both hexagonal closest packed (hcp) and cubic closest packed (ccp) structure types, and isolate the tetrahedral and octahedral holes within each structure type. Lasty, students will be asked to compare and contrast four metal-sulfide unit cells discussed in the paper below.
Powell, A.E., Hodges J.M., Schaak, R.E. Preserving Both Anion and Cation Sublattice Features during a Nanocrystal Cation-Exchange Reaction: Synthesis of a Metastable Wurtzite-Type CoS and MnSJ. Am. Chem. Soc. 2016, 138, 471-474.
In answering these questions, a student will…
- ...develop stronger visualaztion skills for extended, solid state materials;
- ...compare the packing sequence of close packed structures;
- ...locate tetrahedral and octahedral holes in close packed systems;
- ...count the number of tetrahedral / octahedral holes relative to the lattice ions; and
- …determine the number of atoms in a unit cell.
The use of software - such as the demo version of CrystalMaker (http://www.crystalmaker.co.uk) or StudioViewer (Esko - app stores) - will be really helpful. StudioViewer can be run on cell phones, tablets, or MacOS devises. CrystalMaker is available for both Mac and PC.
This learning object was developed at the 2017 MARM IONiC workshop on VIPEr and Literature Discussions. It has not yet been implemented.
This could be assigned for homework, but would likely work better in class with guidance.