Radium bromide the air causes this luminescence. Radium bromide is also very dangerous since the crystals occasionally explode. Helium gas evolved from alpha particles can accumulate within the crystals which cause them to weaken and rupture. Another property of radium bromide is its ability to crystallize from an aqueous solution. It forms a dihydrate, very similar to barium bromide. The chemical radium bromide is not found in nature; it is created. To extract radium from uranium or pitchblende ores, the most common practice is called the Curie method which it involves two major stages. The first stage is a chemical treatment to
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