This study aimed to identify the effect of mobile learning on first-year high school students while teaching them how to build chemical particle models. It examined four dependent variables: academic achievement and behavioral, cognitive, and emotional engagement. Therefore, 20 female students were selected from the first year of high school and trained to utilize a mobile learning tool called Happy Atoms. A quasi-experimental design and a descriptive approach have been applied to interpret this study's results. A pretest and post-test were designed to determine the extent to which students acquire scientific knowledge. In addition, an observation card was prepared and used to record three dimensions of students' engagement (behavioral, cognitive, and emotional). This study showed a positive effect of using the Happy Atoms tool on the student's academic achievement and overall engagement, particularly their emotional involvement. Based on that, using tablets to learn and teach chemistry topics, such as types of chemical links and electronic distribution, is recommended. The study also suggested utilizing other research methods, such as interviews and surveys, for students' perspectives on this learning tool.