There is a growing body of research which explores the nature of explanation in science classrooms. The vast majority of this work highlights the teacher's role as explainer of scientific phenomena, while little has explored the quality of learners' own explanations. This paper helps redress this imbalance by undertaking an analysis of students' explanations related to aspects of chemical structure and bonding. In this paper we set out our results - an analytical framework for exploring the explanations produced by students within the context of a chemistry course. The primary source of data used in this research derives from interviews with students in the U.K. studying chemistry at University entrance level. These interviews were undertaken as part of a longitudinal study of the development of students' understanding of the chemical bond concept. The data collected has been interrogated to develop an analytical model of learners' explanations in chemistry.