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Concept
Radium
Summary
Radium is a chemical element with the symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, but it readily reacts with nitrogen (rather than oxygen) upon exposure to air, forming a black surface layer of radium nitride (Ra3N2). All isotopes of radium are radioactive, the most stable isotope being radium-226 with a half-life of 1,600 years. When radium decays, it emits ionizing radiation as a by-product, which can excite fluorescent chemicals and cause radioluminescence.
Radium, in the form of radium chloride, was discovered by Marie and Pierre Curie in 1898 from ore mined at Jáchymov. They extracted the radium compound from uraninite and published the discovery at the French Academy of Sciences five days later. Radium was isolated in its metallic state by Marie Curie and André-Louis Debierne through the electrolysis of radium chloride in 1911.
In nature, radium is found in uranium ores and (to a lesser extent) thorium ores in trace amounts as small as a seventh of a gram per ton of uraninite. Radium is not necessary for living organisms, and its radioactivity and chemical reactivity make adverse health effects likely when it is incorporated into biochemical processes because of its chemical mimicry of calcium. , other than its use in nuclear medicine, radium has no commercial applications. Formerly, around the 1950s, it was used as a radioactive source for radioluminescent devices and also in radioactive quackery for its supposed curative power. These applications have become obsolete owing to radium's toxicity; , less dangerous isotopes (of other elements) are instead used in radioluminescent devices.
Radium is the heaviest known alkaline earth metal and is the only radioactive member of its group. Its physical and chemical properties most closely resemble its lighter congener, barium.
Pure radium is a volatile silvery-white metal, although its lighter congeners calcium, strontium, and barium have a slight yellow tint.
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Marie Curie
Maria Salomea Skłodowska-Curie (ˈmarja salɔˈmɛa skwɔˈdɔfska kjiˈri; ; 7 November 1867 – 4 July 1934), known simply as Marie Curie (ˈkjʊəri , maʁi kyʁi), was a Polish and naturalized-French physicist and chemist who conducted pioneering research on radioactivity. She was the first woman to win a Nobel Prize, the first person to win a Nobel Prize twice, and the only person to win a Nobel Prize in two scientific fields.
Thorium
Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is light silver and tarnishes olive gray when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high melting point. Thorium is an electropositive actinide whose chemistry is dominated by the +4 oxidation state; it is quite reactive and can ignite in air when finely divided. All known thorium isotopes are unstable. The most stable isotope, 232Th, has a half-life of 14.
Uranium
Uranium is a chemical element with symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium radioactively decays by emitting an alpha particle. The half-life of this decay varies between 159,200 and 4.5 billion years for different isotopes, making them useful for dating the age of the Earth.
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PHYS-450: Radiation biology, protection and applications
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