|Atomic mass||226.0254 amu|
Radium was discovered in 1898. Marie Curie discovered that two common uranium ores, pitchblende and chalcolite were more radioactive than refined uranium. This was the indication that there must be another element, one even more radioactive than uranium, mixed with these ores. Further work indicated the samples actually contained two new elements we now know as radium and polonium. Between 1899 to 1902, Marie Curie continued to dissolve, filter, and repeatedly crystallized nearly three tons of pitchblende, lifting every kilogram by herself. The end of that working marathon was marked by the production of 1/10 of a gram of high grade radium chloride. This was enough to confirm her discovery spectroscopically and determine the exact atomic mass of radium. Detection of the nuclear decay of radium, as indicated by the emanation of alpha, beta, and gamma radiation, was in part responsible for the revolution of physics that occurred between 1895 and 1910, for it had previously thought that atoms were permanent and indestructible entities. Marie Curie was shared the Nobel Prize for chemistry with her husband Pierre Curie for their basic research in radioactivity.
Radium is the heaviest of the alkaline-earth metals. Like the others in the group, radium is metallic and thus a good conductor of electricity. When freshly cut, it has a brilliant white color and, in time, a nitride coating develops. Virtually all radium is derived from the byproducts of uranium refining operations.
Radium is intensely radioactive. It glows in the dark with an eerie bluish light. The handwritten laboratory notes of the discovers are still too radioactive today for safe handling.
In the late 1950s, radium was mixed with a second phosphoresent material such as zinc sulfide to make luminous paint for wristwatches, clocks, and aircraft instrument dials. Shown above is the lumininous mixture of radium bromide and zinc sulfide lused in luminous watch dials. The radium gives off dangerous radiation which causes the zinc sulfide to glow. Recognition of the potential health hazards has forced companies to look for alternative materials for glow-in-the-dark paints.
Radium is used as a portable source of neutron radiation in medicine and industry. Radium is formerly used in cancer therapy.