Radium seventh of a gram of radium. One kilogram of the Earth's crust contains about 900 picograms of radium, and one liter of sea water contains about 89 femtograms of radium. Radium was discovered by Marie Sklodowska-Curie and her husband Pierre Curie on 21 December 1898, in a uraninite (pitchblende) sample. While studying the mineral earlier, the Curies removed uranium from it and found that the remaining material was still radioactive. They separated out an element similar to bismuth from pitchblende in July 1898, that turned out to be polonium. They then separated out a radioactive mixture consisting mostly of two
Modulated neutron initiator the force of conventional explosives. The initiator used in the early devices, located at the center of the bomb's plutonium pit, consisted of a beryllium pellet, and a beryllium shell with polonium between the two. The pellet, 0.8 cm in diameter, was coated with nickel and then a layer of gold. The beryllium shell was of 2 cm outer diameter with wall thickness of 0.6 cm. The inner surface of that shell had 15 concentric, wedge-shaped latitudinal grooves and was, like the inner sphere, coated with gold and nickel. A small amount of polonium-210 (50 curies, 11 mg) was deposited