Recognising the importance, as well as the problematic understanding of models of covalent and ionic bonding, research into issues and instructional responses was designed and conducted for the purpose of enhancement of pedagogical content knowledge related to chemical bonding. Three objectives were set: (a) To determine the Faculty students’ understandings of certain words and symbols used in chemistry instruction and to monitor the pre-service teachers’ awareness of attention needed to be given to the language of chemistry instruction; (b) to research the understanding of covalent and ionic bonding models at all levels of the chemistry education system in Croatia and (c) to develop a method for diagnosis of misconceptions related to covalent and ionic bonding, reconstruction of content knowledge and identification of evidence of growth of PCK amongst pre-service teachers, as well as to research the investigational and instructional potential of this method. With regard to the aims, the research is organized in three parts: in the first, language problems are researched, the second is focused on the understandings of chemical bonding concepts and the third part is dedicated to research into the diagnostic and educational potential of the Open interview (OI) method. Various quantitative and qualitative methods and diagnostic instruments were implemented. High school students, Faculty of Science students and high school chemistry teachers were involved in various stages of the research. It was found that many students involved in this research did not demonstrate satisfactory understanding of the meaning of the technical (science) terms, symbolic representations, and everyday words regularly used in teaching and learning about chemical bonding, or chemistry in general. Faculty students’ perceptions about high school students’ understandings of considered terms are not stable. In the most cases, these perceptions are reflections of their own knowledge. It was found that the EKE (expectation-knowledge-expectation) method could be effective in enhancing students’ awareness of the existence of difficulties with understanding of the words and symbols of chemistry instruction. Inadequate knowledge about covalent and ionic bonding is found at all levels of chemistry education in Croatia. There is evidence of a large number of misconceptions. As well as the confirmed potential of OI for acquisition of PCK, this method has been shown to be effective for identification and rectification of pre-service teachers’ misunderstandings. However, to achieve long-term effectiveness, additional instructional strategies are recommended.