Radioactivity and ionizing radiation are typically not included in lower secondary school curricula. However, these phenomena are present in our daily lives, making it essential to introduce these topics in schools to promote scientific awareness and literacy. Research in science education has demonstrated that active learning strategies can effectively address the challenge of introducing modern physics topics, engaging and motivating students to explore science. We present an innovative STEM-based educational project designed to teach radioactivity in lower secondary schools. We outline the structure of the project and share preliminary results from its implementation in Sardinia, Italy.

Methodology:
The program is structured around three didactic units, each lasting two hours. It follows an inquiry-based pedagogy, incorporating both hands-on and minds-on activities with students working in small teams. Each unit includes an introductory quiz to assess prior knowledge, a game to reinforce key concepts, a brief presentation to introduce new material, and a final quiz to evaluate learning outcomes. The games are progressively more complex and serve to stimulate friendly competition, enhancing team collaboration and knowledge retention.
The first unit begins with a quiz to assess students' understanding of atomic structure, nucleus composition, and isotopes. The accompanying game requires them to build isotopes using colored construction bricks to represent protons, neutrons, and electrons. The presentation introduces the concept of radiation and radioactivity, told through a historical narrative.
The second unit’s quiz explores knowledge of X-rays, radioactivity, cosmic rays, and natural and artificial radiation exposure. The game simulates radioactive decay by using 100 one-cent coins to model the decay process. Teams cast the coins multiple times, recording the number of "undecayed" atoms, and plot the results on a Cartesian plane to visualize exponential decay. The presentation explores radioactive decay modes and their underlying laws, using animations and videos.
The final unit quizzes students on the factors influencing nuclear stability, the strong nuclear force, and radioactive decay types. The game uses a modified “goose game” format, where teams move on an isotope chart, following the decay paths of uranium or thorium, with dice showing alpha and beta decay types. The presentation covers natural radioactivity with a focus on the radon problem.
All the activities include demonstrations of radiation detectors, such as a Geiger counter, a radon monitor, and a solid-state detector able to show the particle tracks. At the end of the three units, a final quiz is administered to assess the overall learning and understanding of the students.

Results and discussion:
The project was carried out in three classes at a school in Sardinia, Italy, with 58 students (34 males and 24 females) taking part. A qualitative analysis of students’ artifacts and assessments indicated that the project effectively promoted critical thinking, teamwork, and scientific awareness on the topics explored. By integrating real-world scientific tools, the project helped connect theoretical knowledge with practical applications. Ultimately, this active and interdisciplinary learning approach provides teachers with a valuable framework for introducing complex scientific concepts to middle school students in an engaging manner.

Keywords: Radioactivity, lower secondary school, hands-on activities, STEM project, quizzes, games, teamwork.