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 closely resemble its lighter congener barium. Pure radium is a volatile silvery-white metal, although its lighter congeners calcium, strontium, and barium have a slight yellow tint. Its color rapidly vanishes in air, yielding a black layer of radium nitride (RaN). Its melting point is either or and its boiling point is . Both of these values are slightly lower than those of barium, confirming periodic trends down the group 2 elements. Like barium and the alkali metals, radium crystallizes in the body-centered cubic structure at standard temperature and pressure: the radium–radium bond distance is 514.8 picometers. Radium has a density