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
Radium (which is mostly Ra) emits mostly alpha particles, but other steps in its decay chain (the uranium or radium series) emit alpha or beta particles, and almost all particle emissions are accompanied by gamma rays. In 2013 it was discovered that the nucleus of Radium-224 is pear-shaped. This was the first discovery of an asymmetric nucleus. Radium, like barium, is a highly reactive metal and always exhibits its group oxidation state of +2. It forms the colorless Ra cation in aqueous solution, which is highly basic and does not form complexes readily. Most radium compounds are therefore simple ionic compounds,