Radium chemicals and cause radioluminescence. Radium, in the form of radium chloride, was discovered by Marie and Pierre Curie in 1898. 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 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 adverse health
Radium of 5.5 g/cm, higher than that of barium, again confirming periodic trends; the radium-barium density ratio is comparable to the radium-barium atomic mass ratio, due to the two elements' similar crystal structures. Radium has 33 known isotopes, with mass numbers from 202 to 234: all of them are radioactive. Four of these – Ra (half-life 11.4 days), Ra (3.64 days), Ra (1600 years), and Ra (5.75 years) – occur naturally in the decay chains of primordial thorium-232, uranium-235, and uranium-238 (Ra from uranium-235, Ra from uranium-238, and the other two from thorium-232). These isotopes nevertheless still have half-lives too short