Atom and Nucleus

Introduction - Radioactivity

In 1896, Henri Becquerel, a French scientist, was studying minerals. He left a piece of uranium ore in his desk drawer on top of a photographic plate wrapped in light-proof paper. When he developed the plate he was surprised to discover that uranium had given some form of energy which passed through the light-proof paper and darkened the film. This form of energy given off by the uranium was called radioactivity. 

It was soon found that a few other very heavy elements were also radioactive. In 1898, after two years of exhausting work, the Curies separated radium and polonium. Radium is several million times more radioactive than uranium. Since radioactivity is not affected by physical or chemical changes, it was realised that it must be a property of the nucleus of the atom. 

• The Nobel Prize in Physics 1903: The Nobel Prize in Physics 1903 was divided, one half awarded to Antoine Henri Becquerel "in recognition of the extraordinary services he has rendered by his discovery of spontaneous radioactivity", the other half jointly to Pierre Curie and Marie Curie, née Sklodowska "in recognition of the extraordinary services they have rendered by their joint researches on the radiation phenomena discovered by Professor Henri Becquerel".

Next: Nuclear Binding Energy

• Atomic Mass Unit

• Binding Energy and Nuclear Stability