Lewis Structures illustrates the basic concepts of G.N. Lewis's representations of the valence shell electronic structures of atoms and molecules. This notation is briefly explained and, after demonstrating the octet rule, the electronic structure of molecules is introduced. The student then learns how to use the concept of formal charge to determine the best Lewis dot representation. More advanced topics such as molecules with expanded octets and electron-deficient molecules complete the module. The user may, at any time, jump directly to any topic or choose to investigate some of the side paths within the module.

Lewis Structures Quiz allows the user to apply the procedures described in Lewis Structures to determine formal charges and the best Lewis representations for molecules and polyatomic ions. There are two sets of highly-detailed questions in this module. The first set asks the student to assign formal charges to the atoms in a Lewis structure. The second set requires the student to find the best Lewis structure given only a skeletal arrangement of atoms and the overall charge on the species. Plenty of advice helps the user in this challenging quiz.

http://www.cem.msu.edu/~gencem/lewis/index.html