Web-based tutorial on VSEPR (Valence Shell Electron Pair Repulsion) Theory for General Chemistry

Authored by Lawrence McGahey, Professor of Chemistry at The College of St. Scholastica in Duluth MN. The tutorial uses rotatable 3D models created and stored in the ChemEd DL (Chemical Education Digital Library).

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This resource is a web-based tutorial for general chemistry students about predicting 3D shapes of covalently bonded species using VSEPR theory. The resource consists of:

  1. an introductory essay that reviews the steps for assigning the geometry about a covalently bonded central atom. This essay incorporates materials from Models 360 and Chem Prime and a link to Periodic Table Live, part of the ChemEd DL (Chemical Education Digital Library).
  2. Also included are two versions of a web-delivered tutorial constructed with the freeware program HotPotatoes (ver 6) by HalfBaked Software. The completed web pages do not require the original program files, but these are included for instructors to modify. The two tutorials use the same questions about the same molecular models. The "long version" of the tutorial breaks down questions into sub-parts which provide feedback at each step before the original question is asked again. The second "short version" does not break the practice question into smaller parts; it merely provides brief feedback to the practice question. Students may go through the tutorials more than once to build mastery.
  3. Finally, a summative assessment quiz is included, but it does not provide explanatory feedback.

Learning Goals

Students will receive feedback in learning to correlate or assign three dimensional structures and their geometrical description to a standard Lewis Structure. The main skills developed are pattern recognition, vocabulary, and interpretation of visual aids.

Context for Use

This activity could be used in lab activity, as out-of-class homework or as an optional study supplement. Students need a java-enabled computer connected to the web. No other special software is needed.

The tutorial is intended to be used after a introduction to molecular geometry and VSEPR in the regular classroom.

Description and Teaching Materials

All the materials are available for download at the Moodle site within the Chemical Education Digital Library (ChemEd DL).(http://moodle.chemeddl.org/course/view.php?id=78).

Teaching Notes and Tips

The instructor first introduces molecular geometry and VSEPR as in a traditional college textbook that relies primarily on 2D or static 3D models. Students then review the basics of VSEPR in a combined 2D and 3D version online. The feedback tutorials are designed to address some of the more common problems students exhibit with the topic, such as matching a 3D shape to a geometrical descriptor or distinguishing terms such as trigonal pyramidal from trigonal planar, etc.

Adopters should check which combination of computer software and web browser give the best viewing experience.


The materials include a gradable-on line assessment quiz. It can be supplemented with an instructor's standard paper assessments.

References and Resources

The ChemEd DL contains many resources for teaching chemistry, inlcuding (but not limited to) multimedia periodic table (Periodic Table Live!), a database of 2D and 3D molecules and properties (Models 360), on-line courses, a chemistry wiki (Chem Prime), and a wealth of resources integrated with specific chemistry textbooks, plus so much more.

The ChemEd DL Summit Resource Course (http://moodle.chemeddl.org/course/view.php?id=78) houses all of the submissions from two-year and four-year college faculty members who have designed resources using the Chem Ed DL (Chemical Educational Digital Library at http://www.chemeddl.org) for use in organic chemistry and general chemistry classrooms and laboratories.

This resource is based upon work supported by the National Science Foundation under Grants No. NSF-DUE 1044239 and NSF-DUE 0937796. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation.