The book is written by well-known French radiochemists. It summarizes for the first time the main characteristics of 104 elements of the periodic system, which were previously contained in various reference manuals or special literature. In describing each element, the authors describe the history of the discovery, its most important physical and chemical properties, isotopic composition, methods of obtaining radioactive isotopes, their nuclear characteristics, as well as the most important areas of their application. When translating, the book is supplemented with tables and reference data (sorption on organic and inorganic ionites, extraction, sensitivity of the radioactive determination, etc.) The book is of great interest to a wide range of readers of chemists, physicists and other specialists; it can also serve as a textbook.