Chemical concepts are very abstract; students find it difficult to explain chemical phenomena by using these concepts. For more than twelve years, we have analyzed the results of the matriculation examinations in Israel (Ben-Zvi & Hofstein, 1996). As a result of these analyses, remedies and models have been developed to help students make the transfer from the macroscopic to the microscopic world by using models and other learning interventions. In addition, this tool is used also for the professional training of chemistry teachers in their daily work (e.g., preparing the students for the matriculation examination). Recently we have started an intensive investigation regarding the teaching and learning of the topic "the chemical bond and the structure of molecules". The main goal of this study is to investigate the difficulties of teaching and learning this concept and to develop models and instructional techniques to provide remedies for these difficulties (Levy Nahum, Hofstein, Mamlok-Naaman, & Bar-Dov, 2004).