Reported is an experiment on instructional episodes organized around the planetary atomic model. The study involved 236 children of eight self-contained classes, four of which were reference classes in each of 3rd, 4th, 5th, and 6th grades. The purpose was to investigate the feasibility of presenting these activities within a cognitive hierarchy as early as the middle elementary grades. The two cognitive objectives were designated as factual-conceptual and inferential, each being further classified into the background category and the category pertaining to the model. The 48-item multiple-choice test used in pre- and post-measurements was at the middle-elementary reading level and subjected to jury validation. Regular non-science teachers conducted the experiment 30-45 minutes daily for a seven-week tenure after completion of a 12-hour training period. Statistical analyses showed the presence of satisfactory results. Further research was recommended for the determination of predictive indices for mental abilities and cognitive achievement, the development of various teacher training modes, study of implementation in schools with varying social-economic-ethnic patterns, and study of the feasibility of presenting other science conceptual schemes in elementary schools. (Diagrams may reproduce poorly). (CC)