Discovery of Radioactivity

Abstract

Abstract The historical period between the discovery of natural radioactivity in 1896 and the production of artificial radioactive elements in 1934, was an extraordinary time when scientists devoted many efforts to understand the basic structure of the atom. Becquerel discovered radioactivity present in uranium salts in 1896. Marie and Pierre Curie identified the existence of two new radio-elements, radium and polonium, present in some uranium and thorium minerals in 1898. Rutherford started to study the properties of the radiation emitted from uranium, and in 1899 he found at least two components in it: alpha-radiation and beta-radiation. Villard revealed that radium salts emitted gamma-rays in 1900. Rutherford and Soddy determined that radioactivity was the spontaneous transformation of thorium into a different element. In 1903 they also established that the process decreased exponentially with time. The announcement of the artificial production of new radioactive elements by Irene Curie and Frederik Joliot in 1934, was preceded by the discoveries of the neutron by Chadwick and the positron by Anderson in 1932.