摘要:AbstractThis article is a part of research for a doctoral thesis about improving teaching, enhancing representations and conceptual change of chemical bonding for grade 10 students (15-16 year-old) in Thailand. The aim of this research is to explore students’ understanding of chemical bonding concepts. The sample consisted of 102 grade 10 students from three secondary schools in Chaiyaphum province in the northeast of Thailand. After studying this topic, the students responded to a 9-item two-tier multiple- choice test bonding (Tan & Treagust, 1999), translated into the Thai language which covered the content of chemical bonding. For the data analysis, we report the percentage of students who choose both parts of the two-tier items. The research findings show how many students have difficulty in understanding the concepts of chemical bonding, and there is more potential for the formation of alternative conceptions. The problems identified with students understanding of the abstract concept of chemical bonding are useful for the design and development pedagogical content knowledge of chemistry teachers in secondary school.