This edition retains the essential of effects of visualization activities in the alternative teaching method on G.C.E (A/L) school students' conceptual understanding of 'Resonance' topic in organic chemistry and inorganic chemistry. The interactions and distinctions between them are important characteristics of chemistry learning and necessary for achievement in comprehensing chemical concepts. Therefore, if the students possess difficulties at one of these levels, it may influence the other. For example, if a student has difficulty on the resonance topic, it may influence in the reaction mechanisms of organic compounds, determination of the order of acidity and basicity of organic compounds and the geometric shapes of some inorganic compounds. Thus, determining and overcoming these difficulties are considered as the primary goal in this book.This book needs of A/L school students and undergraduate students in the university.