In chemistry, building arguments and applying concept knowledge is closely linked to evaluating claims, supporting claims with evidence, and justifying the linkage of evidence to claim with reasoning. However, previous studies revealed that, when building arguments, students experience challenges either in differentiating between argument components, in applying concept knowledge, or in building multivariate arguments. Scaffolding may remediate these challenges by supporting students as they focus on the expected argument structure and/or activate the required concept knowledge. As students enter the classroom with different prior knowledge, supports need to be adapted to students' needs. Thus, we designed a two-part argumentation training. The first partis a diagnostic training, in which students receive training for building arguments while their performance is analyzed. The second part consists of four trainings, adapted to the area in which each student experienced the greatest challenges, e.g., (1) in differentiating between argument components, (2) in applying concept knowledge, (3) in both areas, or (4) in building multivariate arguments. The tasks in the trainings center on building arguments on alternative reaction pathways in organic chemistry and combine a multitude of chemical concepts, such as nucleophilicity, basicity, enthalpy, or entropy. There were 64 students enrolled in an Organic Chemistry II course who participated in the training. Evaluation of the two-part training revealed (a) the effectiveness of the training and (b) how students evaluated the training themselves.