||This work consists of an exploring investigation, in order to inquire about posible students' ideas on modern physics, focused on themes related with radioactivity, atomic structure and nuclear energy. In 1997, argentinian secondary students of the fourth and fifth courses (16 to 18 years old) were inquired on these themes. The results show that these students, from all around the country, have an opinion about radioactive emition, structure of mater and forces produced inside the atomic structure. They also express that nuclear energy exits; but it's observed that scientific concepts like radioactive materials and periods of radioactive decay appear as confused ones, especially in the use and control of nuclear energy. We consider that these themes are brought to school as part of their social culture. The study of these ideas is the first step for designing strategies for classroom transfer to approach students' knowledge to a scientific acceptation.