Resumen de Teaching VSEPR:: The Plastic Egg Model

James P. Birk, Soraya Abbassian

• Valence Shell Electron Pair Repulsion theory is taught best by using models. Although a number of models have been described previously, they suffer from a number of defects, especially in that they require a considerable amount of manipulation by the lecturer and they are not readily available for hands-on use by students. We describe the construction and use of a set of models based on plastic eggs, which afford advantages over the previously described models. The plastic egg models allow users to easily distinguish lone pairs from each other by color coding. The models can be used for molecules with more than one central atom. Free rotation of sigma bonds can be easily demonstrated. Mechanisms for SN1 and SN2 reactions can be depicted, providing a model for the inversion or retention of configuration.