especially for students and professors working in this area. Such periodic relationships nucleate a series of concepts and symbols that make them explicit, such as atomic number,valence,oxidation number, chemical element, chemical symbol , simple and composed substances, and mononuclear and polynuclear molecules. these concepts and the fundamental periodic relationship between Z and V are introduced in chemistry freshman courses in college,provide an opportunity to put some chemical relationships into action in a logical manner, and promote their meaningful learning.