Extended structure

3 Jun 2017
Evaluation Methods: 

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.

Evaluation Results: 

Currently, this activity has not been tested in a classroom.  Please post how your students did!

Description: 

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.

http://pubs.acs.org/doi/abs/10.1021/jacs.5b10624

Learning Goals: 

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.
Prerequisites: 
Corequisites: 
Equipment needs: 

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. 

Instructions on using Studio Viewer to visualize structures on mobile devices are available in the learning object, Visualizing solid state structures using CrystalMaker generated COLLADA files.

 

Implementation Notes: 

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. 

Time Required: 
This will probably take 50 minutes depending on how much work with models you do.
3 Jun 2017

Literature Discussion of "A stable compound of helium and sodium at high pressure"

Submitted by Katherine Nicole Crowder, University of Mary Washington
Evaluation Methods: 

Students could be evaluated based on their participation in the in-class discussion or on their submitted written answers to assigned questions.

Evaluation Results: 

This LO has not been used in a class at this point. Evaluation results will be uploaded as it is used (by Spring 2018 at the latest).

Description: 

This paper describes the synthesis of a stable compound of sodium and helium at very high pressures. The paper uses computational methods to predict likely compounds with helium, then describe a synthetic protocol to make the thermodynamically favored Na2He compound. The compound has a fluorite structure and is an electride with the delocalization of 2e- into the structure.

This paper would be appropriate after discussion of solid state structures and band theory.

The questions are divided into categories and have a wide range of levels.

Dong, X.; Oganov, A. R.; Goncharov, A. F.; Stavrou, E.; Lobanov, S.; Saleh, G.; Qian, G.-R.; Zhu, Q.; Gatti, C.; Deringer, V. L.; et al. A stable compound of helium and sodium at high pressure. Nature Chemistry 2017, 9 (5), 440–445 DOI: 10.1038/nchem.2716.

Corequisites: 
Learning Goals: 

After reading and discussing this paper, students will be able to

  • Describe the solid state structure of a novel compound using their knowledge of unit cells and ionic crystals
  • Apply band theory to a specific material
  • Describe how XRD is used to determine solid state structure
  • Describe the bonding in an electride structure
  • Apply periodic trends to compare/explain reactivity
Implementation Notes: 

The questions are divided into categories (comprehensive questions, atomic and molecular properties, solid state structure, electronic structure and other topics) that may or may not be appropriate for your class. To cover all of the questions, you will probably need at least two class periods. Adapt the assignment as you see fit.

CrystalMaker software can be used to visualize the compound. ICE model kits can also be used to build the compound using the template for a Heusler alloy.

Time Required: 
2 class periods
3 Jun 2017

An ion exchange method to produce metastable wurtzite metal sulfide nanocrystals

Submitted by Janet Schrenk, University of Massachusetts Lowell
Evaluation Methods: 

Evaluation methods are at the discretion of the instructor. For example, you may ask students to provide written answers to the questions, evaluate whether they participated in class discussion, or ask students to present their answers to specific questions to the class.

Description: 

In this literature discussion, students use a paper from the literature to explore the synthesis, structure, characterization (powder XRD, EDS and TEM) and energetics associated with the production of a metastable wurtzite CoS phase. Students also are asked define key terms and acronyms used in the paper; identify the goal of the experiments and determine if the authors met their goal. They examine the fundamental concepts around the key crystal structures available.  

 

Preserving Both Anion and Cation Sublattice Features during a Nanocrystal Cation-Exchange Reaction: Synthesis of a Metastable Wurtzite-Type CoS and MnS

Powell, A.E., Hodges J.M., Schaak, R.E. J. Am. Chem. Soc. 2016, 138, 471-474.

http://pubs.acs.org/doi/abs/10.1021/jacs.5b10624

 

There is an in class activitiy specifically written for this paper. 

Corequisites: 
Learning Goals: 

In answering these questions, a student will be able to…

  • define important scientific terms and acronyms associated with the paper;

  • describe the rocksalt, NiAs, wurtzite, and zinc blende in terms of anion packing and cation coordination;

  • differentiate between the structure types described in the paper;

  • explain the difference between thermodynamically stable and metastable phases and relate it to a free energy diagram; and

  • describe the structural and composition information obtained from EDS, powder XRD, and TEM experiments.

Prerequisites: 
Implementation Notes: 

This learning object was created at the 2017 IONiC Workshop on VIPEr and Literature Discussion. It has not yet been used in class.

Time Required: 
50 minutes
28 Jun 2016

Close Packing Activity

Submitted by George Lisensky, Beloit College
Evaluation Methods: 

This has been used by the author to illustrate features of class packing in lecture. 

Description: 

Many extended structures can be viewed as close-packed layers of large anions, with the smaller cations fitting in between the anions. Larger holes between close-packed anions can hold cations with octahedral coordination. Smaller holes between close-packed anions can hold cations with tetrahedral coordination. The online jsmol resources show these layers and their holes.

Learning Goals: 

Students will understand octahedral and tetrahedral holes between close packing layers (either hcp or ccp)

Equipment needs: 

A physical model kit such as the ICE Solid State Model Kit (see the related activities) could be used. With the linked web resources for this activity students can display individual layers and the holes between them. Both physical and virtual models are valuable learning tools. Either could be used separately depending on availability but they work together well.

Prerequisites: 
Corequisites: 
Implementation Notes: 

For cubic close packing

Click on item 1 and click on Spacefill. Click on item 2 and item 4. What is the arrangement of atoms around each other in Pa, Pb, and Pc layers?

Click on item 1, then item 3, then item 5 to stack layers. The image can be rotated by dragging. You can add or subtract layers by backing up a step or going forward. You can switch between Ball, Spacefill, and Translucent representations.

To repeat the sequence, where should the next layer go? Click on step 6.

Step 7 shows that these layers contain a face-centered cube, stacked along its body diagonal.

Similarly you can experiment by filling in the spaces between the layers. Where can you fit tetrahedra between the packing spheres? Where can you fit octahedra between the packing spheres?

Try switching the display to Ball and Stick with Translucent Polyhedra.

A similar procedure can be used to examine hexagonal close packing.

A note about color: steps with color names in them change the color. Other steps do not. For example if you want the layers different colors use step 1, 2, 4, 7; if you want the layers the same color use steps 1, 3, 5, 6.

Time Required: 
30 minutes
27 Jun 2016

Online Homework for a Foundations of Inorganic Chemistry Course

Submitted by Sabrina G. Sobel, Hofstra University
Evaluation Methods: 

Students are graded on a sliding scale based on the number of attempts on each question. An overall grade is assigned at the end of the semester, adjusted to the number of points allotted for the homework in the syllabus. 

Evaluation Results: 

Student performance on the overall homework assignments for the semester includes questions assigned on General Chemistry topics that are part of this class syllabus. 

 201420152016
Number404741
Average89%80%83%
S.D.15%19%23%

In addition to gethering data on overall  performance, I and my student assistants, Loren Wolfin and Marissa Strumolo, have completed a statistical study to assess performance on individual questions, and to identify problem questions that need to be edited. We identified two separate issues: incorrect/poorly worded questions, and assignment of level of difficulty. Five problematic questions were identified and edited. The level of difficulty was reassigned for eight questions rated as medium (level 2); six were reassigned as difficult (level 3), and two were reassigned as easy (level 1). I look forward to assessing student performance in Spring 2017 in light of these improvements. Please feel free to implement this Sapling homework in your class, and help in the improvement/evolution of this database.

Description: 

The Committee on Professional Training (CPT) has restructured accreditation of Chemistry-related degrees, removing the old model of one year each of General, Analytical, Organic, and Physical Chemistry plus other relevant advanced classes as designed by the individual department. The new model (2008) requires one semester each in the five Foundation areas: Analytical, Inorganic, Organic, Biochemistry and Physical Chemistry, leaving General Chemistry as an option, with the development of advanced classes up to the individual departments. This has caused an upheaval in the treatment of Inorganic Chemistry, elevating it to be on equal footing with the other, more ‘traditional’ subdisciplines which has meant the decoupling of General Chemistry from introduction to Inorganic Chemistry. No commercial online homework system includes sets for either Foundations or Advanced Inorganic Chemistry topics. Sapling online homework (www.saplinglearning.com) has been open to professor authors of homework problems; they have a limited database of advanced inorganic chemistry problems produced by a generous and industrious faculty person. I have developed a homework set for a semester­-long freshman/sophomore level Inorganic Chemistry course aligned to the textbook Descriptive Inorganic Chemistry by Rayner-Canham and Overton (ISBN 1-4641-2560-0, www.whfreeman.com/descriptive6e ), and have test run it three times. Question development, analysis of student performance and troubleshooting in addition to topic choices, are critical to this process, especially in light of new information about what topics are taught in such a course (Great Expectations: Using an Analysis of Current Practices To Propose a Framework for the Undergraduate Inorganic Curriculum: http://pubs.acs.org/doi/full/10.1021/acs.inorgchem.5b01320 ).This is an ongoing process, and I am working to improve the database all the time.

Prerequisites: 
Corequisites: 
Course Level: 
Learning Goals: 

1.      Increase understanding in these topic areas:

a.      Acid-base chemistry and solvent systems

b.      Bonding models of inorganic molecules and complexes

c.      Bonding models in extended systems (solids)

d.      Descriptive chemistry and Periodic Trends

e.      Electronic structure of inorganic molecules, complexes and solids

f.       Extended structures: unit cells and other solid-state structural features

g.      Molecular structure and shape of inorganic molecules

h.      Inorganic Complexes nomenclature, bonding and shapes

i.       Redox chemistry and application to inorganic systems

j.       Thermodynamics as applied to inorganic solids and inorganic systems

2.      Practice using knowledge in these topic areas:

a.      Acid-base chemistry and solvent systems

b.      Bonding models of inorganic molecules and complexes

c.      Bonding models in extended systems (solids)

d.      Descriptive chemistry and Periodic Trends

e.      Electronic structure of inorganic molecules, complexes and solids

f.       Extended structures: unit cells and other solid-state structural features

g.      Molecular structure and shape of inorganic molecules

h.      Inorganic Complexes nomenclature, bonding and shapes

i.       Redox chemistry and application to inorganic systems

j.       Thermodynamics as applied to inorganic solids and inorganic systems

Implementation Notes: 

The database of homework questions is available through Sapling Learning. They can be implemented as an online homework set for a class. Students need to buy access to the Sapling online homework for the duration of the class, typically $45.

Time Required: 
variable
27 Jun 2016

Solid State Stoichiometry Activity

Submitted by George Lisensky, Beloit College
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 and activity answer key in the faculty-only files.

Evaluation Results: 

Most students have been able to explain 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.

Description: 

The goal of this activity is to have students calculate the empirical formula of a compound given the contents of a unit cell. 

A repeating building block, or unit cell, is used to represent extended structures since shifting a unit cell along its edges by the length of the edge will exactly replicate the extended structure.

In determining stoichiometry for an extended structure only the fraction of an atom within the unit cell counts. In three-dimensions atoms can be shared between unit cells on corners, on edges and on faces of the unit cell. Atoms on corners are shared by eight unit cells, atoms on edges are shared by four cells and atoms on faces are shared by two cells. Therefore only one-eighth of a corner atom, one-quarter of an edge atom and one-half of an atom on a face is in any one unit cell. The total number of atoms in a unit cell is given by:

Assignment:

For five solid state structures determine the empirical formula. Show your work by indicating how many spheres of each type have their centers located inside the unit cell, on faces, on edges, or on corners. (A given sphere only has one location: inside, face, edge, and corner locations are mutually exclusive.)

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.

Equipment needs: 

A physical model kit such as the ICE Solid State Model Kit (see the related activities) could be used. With physical models students have to visualize the portion of each atom that is within the unit cell.

With the linked web resources for this activity students can use the "faces" option to shade the faces of the unit cell to help visualize the portion of each atom that is within the unit cell.

Both physical and virtual models are valuable learning tools. Either could be used separately depending on availability but they work together well.

Corequisites: 
Prerequisites: 
Implementation Notes: 

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

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.

Time Required: 
1 hour
27 Jun 2016

Solid State Stoichiometry Online

Submitted by George Lisensky, Beloit College
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.

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. 

 

 
Corequisites: 
Prerequisites: 
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
22 Jun 2016

Visualizing solid state structures using CrystalMaker generated COLLADA files

Submitted by Barbara Reisner, James Madison University
Evaluation Methods: 

I used the SALG (Student Assessment of Learning Gains) to see how much different aspects of the course help their learning. In 2015 (model kits only) and 2016 (model kits and Studio Viewer), I asked about the gains they made in understanding solid state structures. In 2016, I asked how much the model kits and Studio Viewer helped their learning.

Evaluation Results: 

On the end of semester SALG in 2016, I asked students about the solid state model kits and Studio Viewer. “HOW MUCH did each of the following aspects of the class HELP YOUR LEARNING?”

 Solid State Model KitsStudio Viewer
No help2%2%
A little help9%9%
Moderate help2%9%
Much help11%22%
Great help69%58%
Not Applicable2%2%

The students responded more favorably to the solid state model kits, but 80% of students thought that both the model kits and Studio Viewer provided much or great help.

I also asked, "As a result of your work in this class, what GAINS DID YOU MAKE in your UNDERSTANDING of each of the following?" Here are student responses for extended (solids) structure

 Spring 2016Studio Spring 2015
No gains2%-
A little gain7%10%
Moderate gain7%6%
Good gain36%41%
Great gain33%29%
Not Applicable-2%

As you can see, there are not great differences between the year I used Studio Viewer (Spring 2016) and the year I used only model kits.

I gave students the option of using it to help them complete an exam question and ~25% of my students used it on the exam. (Students who used the viewer were more likely to get the problem correct because using the viewer removed the ambiguity of where atoms in the unit cell could be found.)

Description: 

Although I’m a solid state chemist, I still find it difficult to teach the visualization of solid state structures. I’m interested in any tool that helps my students visualize solids. My experience is that the more representations students can master, the more likely they are to find one that helps them understand solid state structures.

I’ve used many tools. These include

  • plan diagrams
  • static 3D models (generated by CrystalMaker)
  • CrystalMaker files on a computer (I have a license for my laptop)
  • online sites like ChemTube3D
  • ICE Solid State Model Kits

I believe that it’s important to guide students as they explore 3D extended structures. Since there is no lab directly associated with my class, all of our visualization activities are done in a standard lecture room during one or more 50-minute class periods. While students can work with the free demo version of CrystalMaker on a computer, most students don’t bring their computers to class. However, most students have smartphones and tablets.

This activity describes how to generate DAE files (3D interchange file format). These files can be opened on student devices so that students can individually work with 3D models of extended solid state structures. 

Corequisites: 
Topics Covered: 
Prerequisites: 
Learning Goals: 

A student will be able to use alternate representations of extended solids to better visualize solid state structures.

Implementation Notes: 

I recommend that students download Studio Viewer and the Canvas (LMS) App before class. I also recommend that they practice getting files from Canvas to Studio Viewer before they come to class. (In the future, I will ask them to move all of these files to Studio Viewer prior to class.)

To streamline the transfer process, I make a single page that contains all of the DAE files so students only need to go to a single page on the LMS.

I’ve attached a few DAE files here. You can find many more with the associated LO, “A model for every student: Visualizing solid state structures”.

 

Time Required: 
Highly variable!

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