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Symmetry Elements and Operations
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Albert W. M. Lee, K. M. Leung, Daniel W. J. Kwong, and C. L. Chan
Hong Kong Baptist University, Kowloon Tong, Hong Kong |
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Note: |
This program is included in the Advanced Chemistry Collection (SP-28).
To Order Advanced Chemistry Collection |
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Symmetry Elements and Operations is a multimedia presentation that illustrates the basics of symmetry with three dimensional molecular models and simple text explanations. Three-dimensional graphics and animations are used to define and characterize the symmetry elements commonly encountered in chemical structures. They include identity (E), inversion center (i), proper rotation axis (Cn), plane of symmetry (s), and improper (rotation-reflection) axis (Sn). Symmetry is an important concept in chemistry. A firm understanding of the basic concept of symmetry is extremely useful in studying molecular structure, stereochemistry, spectroscopy, group theory, and reaction mechanisms. Often it is difficult and requires quite a bit of imagination to visualize the symmetry properties within a molecule presented on a two-dimensional printed page. Use of molecular models may help, but such models are typically difficult for students to see when demonstrated by an instructor in the classroom. Symmetry Elements and Operations was designed to help students identify the symmetry properties of a particular structure by performing onscreen symmetry operations and then comparing the structure of the molecule before and after the symmetry operation. The screens can be easily projected using a large monitor or a LCD panel or projector for classroom use. Symmetry is generally first introduced in organic chemistry when stereochemistry and optical isomerism are discussed. Only simple symmetry elements such as point of symmetry (i) and plane of symmetry (s) are usually discussed at that level. A more thorough treatment is done in inorganic and/or physical chemistry courses when point group classification and group theory are introduced. Symmetry Elements and Operations can be used at either the introductory or more advanced level. Organic, inorganic, and organometallic molecules are used as examples. In Symmetry Elements and Operations, definitions of each symmetry element with specific molecules are presented first as examples. Second, the symmetry operations with reference to the symmetry elements within a molecule can be carried out onscreen. For example, rotations around a Cn axis or reflection across a plane are animated using three-dimensional models. Finally, several examples (cyclopropane, NH3, SF6, and H2O2) are used to give the student additional practice in identifying symmetry elements and their respective operations. In the sections on each individual symmetry element, the symmetry operations concerned are treated in detail with full illustration to build up the basic concepts. However, in the Example Section, some additional symmetry elements are present that are not dealt with in the program. These are labeled without full illustration. Students should be able to identify these additional symmetry elements by applying the basic concepts learned in previous sections. Hardware and Software Requirements Software in Series C of JCE: Software requires an Apple Macintosh computer with 4 MB RAM, a hard drive, and a SuperDrive floppy disk drive. System software version 7 or later is required. In addition, Symmetry Elements and Operations requires approximately 4 MB of free space on a hard drive; a color monitor capable of displaying at least 256 colors at 640 3 480 resolution (13-in. or larger monitor). |
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Last Updated: July 19, 2001 Created: |
Created by: S. B. Mathews Comments to: jceonline@chem.wisc.edu |
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| © 1997 Division of Chemical Education, Inc., American Chemical Society. All rights reserved. | |