Marie Curie Discovers Radium
In December 1898, Marie Curie and her husband Pierre announced the discovery of radium, a new and intensely radioactive element, working in Paris. Together with polonium, which they had reported earlier that year, it transformed scientists' understanding of the atom and opened the way to nuclear physics and radiation medicine. The summary's wording is a little compressed: the elements were announced in 1898, but Curie did not isolate pure radium until 1902, and her Nobel Prizes came later.
The background lay in the mid-1890s. In 1895 Wilhelm Röntgen discovered X-rays, and in 1896 Henri Becquerel found that uranium salts emitted penetrating rays without any external energy source. Curie, a Polish-born physicist who had moved to Paris to study, chose this puzzling phenomenon as her doctoral research. Using a sensitive electrometer developed by Pierre and his brother Jacques, she measured the faint electrical effect of the rays and coined the term "radioactivity." She concluded that the emission was a property of the atoms themselves, an idea that challenged the notion of the atom as indivisible and unchanging.
Curie noticed that pitchblende, a uranium ore, was more radioactive than the uranium it contained could explain. She reasoned that it must hold some other, stronger source. Pierre set aside his own work to join her, and in July 1898 they announced polonium, named for her homeland, then radium in December. Many chemists remained skeptical until the element could be seen and weighed. Over several years, in a poorly equipped shed, Marie processed tons of ore residue by laborious chemical separation, and in 1902 she obtained a tiny quantity of nearly pure radium chloride and determined its atomic weight.
Recognition followed. In 1903 the Nobel Prize in Physics was shared by Marie, Pierre and Becquerel, making Marie the first woman to win a Nobel Prize. After Pierre's death in a street accident in 1906, she took over his professorship at the Sorbonne, becoming its first woman professor, and in 1911 she won the Nobel Prize in Chemistry. She remains the only person to win Nobel Prizes in two different sciences.
The consequences were wide. Radium was soon used to treat cancers and other conditions, laying foundations for radiotherapy and nuclear medicine, and it fueled a commercial craze for radioactive products, some of them harmful. During World War I Curie helped develop mobile X-ray units for field hospitals. The dangers of radiation were poorly understood, and she died in 1934 of a blood disorder, probably aplastic anemia, widely linked to long exposure. Her notebooks remain radioactive today. The Curie name endures through the Radium Institute in Paris, now the Institut Curie, and through the unit of radioactivity named in the family's honor.