Radium
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Radium is a chemical element; it has 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, bu
Radium electroplated on a very small sample of copper foil and covered with polyurethane to prevent reaction with the air
Radium-226 radiation source. Activity 3300 Bq (3.3 kBq)
Marie and Pierre Curie experimenting with radium, a drawing by André Castaigne
Glass tube of radium chloride kept by the US Bureau of Standards that served as the primary standard of radioactivity for the United States in 1927.
Francium
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Francium is a chemical element; it has symbol Fr and atomic number 87. It is extremely radioactive; its most stable isotope, francium-223, has a half-life of only 22 minutes. It is the second-most ele
Radium
…Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium…
This sample of uraninite contains about 100,000 atoms (3.7×10−17 g) of francium-223 at any given time.