This study was designed for two major goals, which are to describe students' mental models about atom concept from 6th to 8th grade and to compare students' mental models with visual representations of atom in textbooks. Qualitative and quantitative data were collected with 4 open-ended questions including drawings which were quantified using the Evaluation Rubric for Atomic Model Representations. Descriptive statistics were also used to describe students' mental models and textbook visual representations. The study was implemented in two elementary schools in Istanbul, Turkey with 90 students. In addition, 251 visuals from the science and technology textbooks were evaluated in the study. The results indicated that Dalton's Atomic Model was seen as the most frequent model in both the students' drawings and textbook atom visuals. However, the results were different in the each grade level. In addition, qualitative results show that motion was not frequently seen in students' drawings nor textbooks visuals. (Contains 18 figures and 10 tables.)