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CHEM202: Advanced Inorganic Chemistry

Unit 1: Symmetry   The concept of symmetry is critical to understanding certain physical properties of metal compounds, such as vibrational modes.  In this unit, we will discuss specific symmetry elements, including reflection planes, rotation axes, and inversion centers.  While a molecule can have many symmetry elements, some will specifically determine the molecule’s physical properties.  This unit teaches you how to assign symmetry elements and point groups to a given molecule.  You will learn to interpret the character tables, which will help you prioritize symmetry elements and classify molecules according to their respective point groups.  Note that certain characteristic properties of molecules, which may include polarity, chirality, and vibrational mode, correspond to each point group.  Character tables will allow you to identify spectroscopic properties of the compounds.     

Unit 1 Time Advisory
This unit should take you approximately 7.5 hours to complete.

☐    Subunit 1.1: 2.0 hours

☐    Subunit 1.2: 1.0 hour

☐    Subunit 1.3: 2.0 hours

☐    Subunit 1.4: 2.5 hours

Unit1 Learning Outcomes
Upon successful completion of this unit, the student will be able to: - Identify elements of symmetry in molecules. - Determine molecular point groups using a symmetry flow chart. - Use character tables to explain spectroscopic properties of molecules. - Predict allowed and forbidden transitions of molecules. 

1.1 Symmetry Elements, Group Theory, and Irreducible Representations   - Web Media: YouTube: Mechanophore’s “Elements of Symmetry” Link: YouTube: Mechanophore’s “Elements of Symmetry” (YouTube)
 
Instructions: Please watch the video (runtime = 5:38 minutes).  This video illustrates the three basic elements of symmetry.  Please note that there are more than three point groups; however, some arise from a combination of the three basic elements.  (For example, an improper rotation, S, arises from a rotation, C, combined with a mirror plane, ?.)
 
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  • Reading: UC Davis: ChemWiki’s “Group Theory: Theory” Link: UC Davis: ChemWiki’s “Group Theory: Theory” (HTML)
     
    Instructions: Please read the entire webpage.  Once you have familiarized yourself with the symmetry elements and terminology, the bulk of information can be condensed into the flowchart presented in Table 2.12.  Please follow the link under the “Symmetry Point Groups” section for more information on each of the individual point groups.

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1.2 Point Groups and Schoenflies Notation   - Reading: The International Union of Crystallography: L. S. Dent Glasser’s “Symmetry” Link: The International Union of Crystallography: L. S. Dent Glasser’s “Symmetry” (HTML)
 
Also available in:

[PDF](http://www.mx.iucr.org/iucr-top/comm/cteach/pamphlets/13/13.pdf)  
    
 Instructions:  Please read all sections.  This material may also be
downloaded as a PDF in pamphlet form.  Point groups are primarily
used by crystallographers for symmetry notation in place of the
group theory methods described previously.  Also note that
Schoenflies notation is an older notation system and is listed
alongside the Hermann-Mauguin notation as such.  
    
 Terms of Use: Please respect the terms of use displayed on the
webpage above.

1.3 Character Tables   - Reading: UC Davis: ChemWiki’s “Character Table” Link: UC Davis: ChemWiki’s “Character Table” (HTML)
 
Instructions: Please read the entire webpage.  Also, please work through the questions pertaining to BF3 at the bottom of the page.  These questions will guide you in understanding the type of information obtained from character tables. 
 
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1.4 Using Group Theory and Character Tables   - Reading: UC Davis: ChemWiki’s “Group Theory and its Application to Chemistry” Link: UC Davis: ChemWiki’s “Group Theory and its Application to Chemistry (HTML)
 
Instructions: Please read the material covered in the first five sections (up to and including 5.3).  This material explains how group theory is applied.  Follow the example of ammonia provided.  The first external link provides an interesting video demonstration of solving the Rubik’s cube based on the group theory discussion provided.    
 
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  • Assessment: University of Rhode Island’s “Chemistry 401: Symmetry and Point Groups—Practice Problems” Link: University of Rhode Island’s “Chemistry 401: Symmetry and Point Groups—Practice Problems” (HTML)
     
    Instructions: Please work through problems 1–4.  The answers are provided by clicking on the links at the end of each question.
     
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