The concepts of atom and molecule are included in both physics and chemistry subjects and therefore learners acquire knowledge from both fields via various sources. This situation causes them to develop different approaches when they encounter questions on related topics. In addition, since the concepts of atom and molecule are two intertwined concepts, understanding the differences between them sometimes causes difficulties. Therefore, this study was conducted to determine the approaches of 4th grade pre-service physics teachers about hydrogen and helium atoms and molecules. With the data obtained, it is aimed to reveal the learning difficulties experienced in the related subject.

The research question of the study is as follows:

What are pre-service physics teachers' approaches to the concepts of hydrogen and helium atoms and molecules?

This is a qualitative study conducted with the participation of 26 pre-service physics teachers. The entire sample was selected from those who had taken and succeeded in the Modern Physics course. The aim of the study was to determine how the participants envisioned hydrogen and helium atoms and molecules. Each participant was asked to draw and explain the related concepts. Subsequent analyses aimed to determine pre-service teachers' approaches to these concepts.

In the analysis, it was seen that the pre-service teachers were predominantly influenced by the Bohr model. For the representation of molecules, it was determined that there were drawings similar to the representations in the literature (Taber, 2002). It was noticed that sometimes the pre-service teachers used lettering and sometimes they used symbols. However, as stated by Harrison and Treagust (2000), students cannot interpret scientific analogical models as intended or have difficulty in understanding these models.

Taber, K. S. (2002). Chemical Misconceptions: Prevention, Diagnosis and Cure. Harrison, A. G., & Treagust, D. F. (2000). Learning about atoms, molecules, and chemical bonds: A case study of multiple-model use in grade 11 chemistry. Science Education, 84(3), 352-381.