Radioactivity was discovered by the French physicist Henri Becquerel.
Core answer
In 1896, Henri Becquerel found that uranium salts emitted a penetrating radiation that could fog photographic plates even when they were wrapped in opaque paper. This showed that the emission was a spontaneous property of the uranium itself, and this phenomenon became known as radioactivity.
Role of the Curies
Soon after Becquerel’s discovery, Marie and Pierre Curie began a systematic study of these new rays. They coined the term “radioactivity,” measured its intensity, and discovered additional highly radioactive elements, including polonium and radium.
