Education sciences research Works are unanimous on the fundamental role of conceptions to organize and facilitate a learning situation of a scientific concept. The objective of this work is to detect the conceptual universe of students, at the end of license cycle, relatively to chemical bond concept and its associated concepts like valence and octet rule and to compare the students’ responses at the beginning and end of this cycle. The purpose is to see, after intense courses on those concepts, what are the definitions and models appropriated by students and how they design it. To do this, we asked 50 students, subjects of our study, to express their definitions of the chemical bond, valence and octet rule. The data analysis has shown that there is still confusion and amalgams about this concept and its associated concepts.