Bonding models: Extended systems

13 Jun 2018

The Preparation and Characterization of Nanoparticles

Submitted by Kyle Grice, DePaul University
Evaluation Methods: 

Students are evaluated on their participation in lab, lab safety, lab notebook pages, and a lab report turned in a week after the last day of the experiment. 

Evaluation Results: 

This lab was first run in spring of 2016, and again in spring of 2017 and 2018 (a different instructor carried out the lab in 2018). 

In general, students do well on the lab report and seem to enjoy the experiment.They often need guidance when interpreting the Analytical Chemistry article and selecting the correct equations. Discussing their values with them in office hours ("does that make sense?") helps them understand their calculations. 

A sample lab report that scored above 90% is included in the faculty-only files. 

Description: 

This is a nanochemistry lab I developed for my Junior and Senior level Inorganic Chemistry course. I am NOT a nano/matertials person, but I know how important nanochemistry is and I wanted to make something where students could get an interesting introduction to the area. The first time I ran this lab was also the first time I made gold nanoparticles ever! 

We do not have any surface/nano instrumentation here (AFM, SEM/TEM, DLS, etc... we can access them at other universities off-campus but that takes time and scheduling), so that was a key limitation in making this lab. 

While it was made for an upper-division course, I think It could be adapted and implemented at many levels, including gen chem. I do not spend much time on nano in the lecture (none in fact), so this lab was made to have students learn a bit about nanochemistry somewhere in inorganic chemistry. We have one 10-week quarter of inorganic lecture and lab, offered every spring quarter.

This lab takes approximately 2-3 hours if students are well prepared and using their time well, but is usually spread over 2 days. Students are concurrently doing experiments for another lab or two because we have a lab schedule that overlaps multiple labs, and can do these during one day or across two days. The lab space is an organic chemistry laboratory, so we have access to the usual lab synthetic equipment

Students in thelaboratory write lab reports,which are the due the week after the last day of the lab experiment. In the lab report they use their UV-Vis data to calculate information about the AuNP. 

The lab has been posted, as well two photos from students' ferrofluids (these were posted with permission on our departmental blog). A rubric has been posted as a faculty-only file. I have also included a student submission that received over 90% on the lab with their identifying information removed. Students write and introduction and need to cite journal articles in their report, so they are expected to do reading on nanochemistry topics outside of the lab period as they write their reports. 

I am sure the lab can be improved, this was what i came up with the materials and time I had. I plan on continuing to revise and edit it as time goes on. Any suggestions are very welcome! 

Prerequisites: 
Corequisites: 
Learning Goals: 

A student should be able to perform a chemical laboratory experiment safely and follow proper lab notebook protocol.

A student should be able to determine the average size of AuNPs from spectroscopic data and primary literature.

A student should determine atomic and nano-scale information from physical properties.

A student should be able to construct a lab report in the style of an ACS article (Students in my lab wrote lab reports for each experiment). 

Equipment needs: 

For this experiment, you  need

The chemical materials - HAuCl4, trisodium citrate, 

Heating/stirring plates

Glassware

UV-Vis spectrometer (mainly Vis)

A laser pointer

Strong magnets (the stronger and larger the better)

Implementation Notes: 

The syntheses are relatively straightforward, although we've had some problems getting "spikes" for the ferrofluid. Anecdotally, adding the reagents and doing the steps faster tends to give better "spiking". Some students just see a blob moving around in response to the magnet, which was fine in terms of their report. 

The AuNP synthesis can also be done with an ultrasonicator or by addition of sodium borohydride, among other methods. We don't have them make a calibration curve of chloride addition, but that could be a possibility.  

I like having a pre-made solution of a red oroganic dye to shine the laser pointer through to compare versus the laser shining through the AuNP solution. 

One year, the AuNP synthesis was going very slow. We realized it was because the Au(III) was diluted in acid, so it was protonating the citrate. Boiling for a while before adding the citrate solution helped fix this problem.

KAuCl3 is also a good source of Au(III) for this lab. 

Time Required: 
2 hours
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
10 Apr 2017

Redox Chemistry and Modern Battery Technology

Submitted by Zachary Tonzetich, University of Texas at San Antonio
Evaluation Methods: 

I do not grade this activity, but if I did, I would look for class participation in the discussion or assign several of the questions to be turned in at a later date.

Evaluation Results: 

My impression of this activity is that it really helps students see the value of redox chemistry. In my experience, the aspects of redox chemistry we teach students (balancing equations, calculating cell potentials, etc.) seem both difficult and esoteric. This activity reinforces these concepts while demonstrating their importance to modern life. One of the biggest realizations the students come to is the relationship between cell voltage and the mass of the materials involved in the redox reaction.

Description: 

This In-Class Activity is a series of instructor-guided discussion questions that explore lithium-ion batteries through the lens of simple redox chemistry. I use this exercise as a review activity in my Descriptive Inorganic Chemistry course to help prepare for examinations. However, my primary purpose with this exercise is to impress upon students how basic concepts in redox chemistry and solid-state structure are directly relevant to technologies they use everyday. I do not focus too heavily on the design or operation of the batteries themselves, as other exercises published on VIPEr already do a very good job of that. My intention is to demonstrate how a basic knowledge of redox chemistry is the first step in understanding seemingly complex technologies.

Learning Goals: 

The primary goal of this In-Class Activity is for students to solidify their understanding of redox reactions, cell voltages and the relationship between electrical energy and potential. The exercise is also designed to show students how these considerations are part of the design of modern batteries. A secondary aspect of the activity explores the solid-state structure of metal-oxides and how these materials are important to the operation of the battery. At the conclusion of the activity, the student should be familiar enough with calculaing cell voltages and free energy changes that they can critically evaluate the components of a standard battery.

Equipment needs: 

None.

Course Level: 
Prerequisites: 
Corequisites: 
Implementation Notes: 

I display the pdf file on screen and use the white board to work out simple arithmetic aspects of the exercise, while soliciting responses from the class.

Time Required: 
45 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.

Corequisites: 
Prerequisites: 
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.

Prerequisites: 
Corequisites: 
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
16 May 2016

Metal and Ionic Lattices Guided Inquiry Worksheet

Submitted by Adam R. Johnson, Harvey Mudd College
Evaluation Methods: 

I walked through the classroom and guided the students as they worked in pairs or groups of three. All the answers were in prior assigned reading from their text so if they were confused, they had that to look at later.

Evaluation Results: 

Some students had trouble seeing some of the holes in the simple lattices, so it was helpful that I was walking around to show them the holes. It was good to have students work together becasue some students were able to see the holes in the geometries and help their partners.

Description: 

This is a short worksheet that guides students through simple metal lattices (SCP, CCP, HCP) and how filling holes in these lattices results in ionic lattices (NaCl, CsCl, fluorite, etc.).

The worksheet was used as an in-class activity after students had read about the material in the text. This activity is probably suitable for first-year students, though I used it with juniors/seniors.

Learning Goals: 

Students will be able to do the following:

for simple lattices:

draw the lattice

determine how many atoms per cell

determine the coordination number, CN, of an atom

locate common holes and describe their CN

calculate the % of space filled up by the atoms

 

For ionic solids:

draw the lattice and count the number of ions in the cell

relate to a simple lattice by hole-filling

determine the # and CN of both cations and anions

Equipment needs: 

none, though a box of pennies or marbles or ping pong balls might be helpful to visualize closest packing. Having models or computer models would have been helpful to show on a screen at the front of the room. rotatable cif files would be especially good, and next time I do this I will prepare cif files or crystalmaker files and upload them here.

Corequisites: 
Prerequisites: 
Implementation Notes: 

This was a bit too long for a 50-minute class period but students finished it up at home. The students who had spent the time reading the book before class definitely did better on the exercise than those who were clearly doing it for the first time in class. Students struggled a bit with the geometry/trig calculations.

Were I to do this again, I would have 3-d rotatable structures available (cif files or crystalmaker files) to help students with the visualization.

Time Required: 
1-1.5 50 minute class periods

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