Radium is about one million times more active than uranium. A single gram of radium-226 will produce 0.000l milliliters of radon a day. teaching what he knew best.-Marie Curie The Governess The close relationship between Manya and her sister Bronya, shown here in 1886, continued throughout their lives. Radium is used to produce radon, a radioactive gas used to treat some types of cancer. The Marie Curie Radium Campaign 67 A World Center for the Study of Radioactivity 69 Physical Decline 71 Jean-Frédéric Joliot (1900-1958) and Irène Curie (1897-1956) 73. A mixture of radium and beryllium will emit neutrons and is used as a neutron source. Radium had been used to make self-luminous paints for watches, aircraft instrument dials and other instrumentation, but has largely been replaced by cobalt-60, a less dangerous radioactive source. It is equal to the number of atoms in a one gram sample of radium-226 that will decay in one second, or 37,000,000,000 decays per second.

The Curie, a unit used to describe the activity of a radioactive substance, is based on radium-226. It decays into radon-222 through alpha decay or into lead-212 by ejecting a carbon-14 nucleus. Radium's most stable isotope, radium-226, has a half-life of about 1600 years. Today, radium can be obtained as a byproduct of refining uranium and is usually sold as radium chloride (RaCl 2) or radium bromide (RaBr 2) and not as a pure material. One ton of uranium ore contains only about 0.14 grams of radium. Curie needed to refine several tons of pitchblende in order to obtain tiny amounts of radium and polonium, another radioactive element discovered by Curie. She reasoned that pitchblende must contain at least one other radioactive element. Marie Curie obtained radium from pitchblende, a material that contains uranium, after noticing that unrefined pitchblende was more radioactive than the uranium that was separated from it. Radium was discovered by Marie Sklodowska Curie, a Polish chemist, and Pierre Curie, a French chemist, in 1898.

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