This study aimed to examine the impact of years of experience and field of expertise on the development of chemistry knowledge structures from STEM experts comprising 103 professors, 10 postdocs, and 146 doctoral students. Of these participants, 127 were specialized in chemistry and the rest were from various science and engineering disciplines. Although most participants were part of a research university located in Northern California, the pool included a small group of experts from different universities and countries. The main source of the data was a Word Association Test generated with 17 keywords that refer to major topics or concepts commonly introduced in the general chemistry curricula. The knowledge structures were examined to determine if the contents and the orientations of the clusters varied between the expert groups. In addition, their analysis was enriched with the consideration of chemistry triplet designations and central terms identified by eccentricity values on each structure. The overall expert knowledge structure generated in this study was also compared to undergraduate structures determined by using the same instrument and methodology. The investigation of the structures revealed several differences between expert groups and provided insight into the transformation of novices into experts. The paper also presents practical suggestions for educators on how to utilize structures while teaching, informing their instructional practices, and reforming teaching materials.