Marie and Pierre Curie were the husband and wife team who became famous for their early investigations into radioactivity (a term introduced by Marie Curie) and who discovered the radioactive elements polonium and radium. It was Henri Becquerel's discovery of radioactivity that first inspired Marie Curie to study this phenomenon for her doctoral thesis. She used a piezoelectric crystal electrometer to search for elements that emitted ionizing radiation and this led to her discovery that the chemical element thorium was radioactive. The electrometer had been built by her husband, Pierre, who in 1880 discovered piezoelectricity and who concentrated on this and magnetism until he joined his wife in her search for new radioactive elements. This search had been stimulated after Marie discovered that the radioactivity of pitchblende (a brownish-black mineral) was much greater than its uranium and thorium content suggested. Unaware of the harmful effects of radiation, the Curies began their search and in July 1898 announced the discovery of polonium (named after Marie's home country of Poland). In December of the same year, they announced the discovery of radium and went on to produce about a gram of pure radium chloride from eight tonnes of waste pitchblende. The Curies and Becquerel shared the Nobel Prize for Physics in 1903 for their work on radioactivity, the same year that Marie became the first woman in France to be awarded an advanced scientific research degree. In 1906 Pierre Curie was killed when he was knocked down by a horse-drawn carriage. Marie continued her work on radioactivity and in 1911 was awarded the Nobel Prize for Chemistry for her discovery of polonium and radium. During the First World War, Marie helped equip ambulances with X-ray equipment, which she herself helped drive to the front line. In the late 1920s she began to suffer from leukaemia, probably due to her long exposure to radiation, and died a few months before her daughter and son-in-law (Irène and Frédéric Joliot-Curie) announced their discovery of artificial radioactivity. In 1995 the Curies were honoured by the French nation by interment in the Paris Pantheon.
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