This study investigated the effectiveness of a web-based learning environment in enhancing 10th grade high-school students' understanding of the concept of "chemical bonding". Two groups participated in this study: an experimental group (N = 161) and a comparison one (N = 93). The teachers in the experimental group were asked to implement four activities taken from a website, all dealing with the concept of "chemical bonding". Computer-based visual models are utilized in all the activities in order to demonstrate bonding and the structure of matter, and are based on student-centered learning. The study incorporated both quantitative and qualitative research. The quantitative research consisted of achievement questionnaires administered to both the experimental and comparison groups. In contrast, the qualitative research included observations and interviews of students and teachers. Importantly, we found that the experimental group outperformed the comparison group significantly, in the achievement post-test, which examines students' understanding of the concept of "chemical bonding". These results led us to conclude that the web-based learning activities which integrated visualization tools with active and cooperative learning strategies provided students with opportunities to construct their knowledge regarding the concept of "chemical bonding". (Contains 4 tables and 2 figures.)