This paper reports the results of applying a particular analytical perspective to data from an interview study: a typology of learning impediments informed by research into learning and students' ideas in science. This typology is a heuristic tool that may help diagnose the origins of students' learning difficulties. Here it is applied to data from students interviewed about a problematic curriculum topic--the "oribital" model of atomic and molecular structures. Several specific features of learners' developing ideas about atomic and molecular structures were identified in published reports of the study. In this paper, interview data is examined "through" the analytical lens of the typology to explore possible explanations for students' learning difficulties in the topic. It is suggested that the typology provides a useful perspective for exploring some aspects of students' learning difficulties, but that the previously published form of the typology could be modified to include important additional types of learning impediments. The heuristic value of the typology is demonstrated in terms of the way that the analysis can both inform teaching, and suggest a focus for further research.