Radium

Radium is a highly radioactive alkaline-earth metal discovered by Pierre and Marie Curie in 1898, extracted from pitchblende. Historically, its most famous use was in luminous paint: radium salts were mixed with a phosphor and applied to watch dials, aviation instruments, and instrument pointers so that the hands glowed in the dark. Owing to the severe radiation hazard, such paints were phased out entirely by the mid-twentieth century. Today radium serves only as a radioactive standard source and as a subject of nuclear physics and radiochemistry research. In nature it occurs mainly as a companion of uranium ores and is no longer mined or used on its own.

Radium compounds are mainly radium chloride (RaCl2) and radium bromide (RaBr2), which were once produced in small quantities together with luminous paint. They are now prepared only in trace amounts in laboratories for source calibration and scientific research, and are not sold as consumer products.