ABSTRACT
The year of 1996 witnessed the 100th anniversary of the discovery of radioactivity which gave birth to nuclear physics — scientific basis of the atomic industry. The basic discoveries made by Becquerel, Pierre and Marie Curie, Thompson, Rutherford, and their successors are reviewed comprehensively in
11]. As early as March 1896 H . Becquerel published his first paper devoted to
some properties of invisible rays emitted by uranium salts. In late 1897 M . Sklodowska-Curie took interest in the newly discovered uranium or Becquerel rays. When she established the fact that uranium and thorium emitted Becquerel rays, she wrote: "I called the capability of emitting such rays the radioactivity1
thus introducing a new term which has since then become conventional in science." Radiating elements were called radioéléments, the term coined from the Latin word radius meaning a ray. It is commonly understood by the scientific community that Becquerel discovered radioactivity in 1896, and the year 1898 is supposed to be when M . Curie introduced the term radioactivity. In 1898 when studying the radiation of already known uranium and thorium compounds, the Curie couple discovered two new elements. On July 18, 1898, they reported the discovery of polonium, and on December 26, 1898, the discovery of radium. In 1899 M . Curie rejected a proposed identity between Becquerel rays and Roentgen rays discovered in 1895. She emphasized that the radioactivity phenomenon is accompanied by mass loss of the source material and permanent energy loss of the radioactive material.
