Radium: properties, history, uses and health effects

Physical and chemical properties

Pure radium is a silvery-white metal that oxidizes and tarnishes quickly in air, often darkening on exposure to nitrogen. As an alkaline earth metal it is chemically reactive, forming compounds such as radium chloride and radium sulfate. Its chemistry resembles that of barium but differs in details because of its radioactivity and larger atomic size. For context on the group to which it belongs, see resources about alkaline earth metals here.

Discovery and historical development

Radium was isolated and identified in 1898 by Marie Curie and Pierre Curie while they were investigating radioactive substances extracted from pitchblende. Their work followed and extended earlier discoveries of radioactivity by others; the Curies recognized a new element present in uranium ores and produced radium salts such as radium chloride. For biographical and historical information about the discoverers, see the pages for Marie Curie and Pierre Curie.

Uses and applications

Early in the 20th century radium was used for its luminescent properties and as a source of radiation in medicine. Its historical applications included luminous dials and scientific instruments and, later, targeted radiotherapy. Modern practice has largely replaced radium with safer isotopes and synthetic sources because of radiological risks.

• Historical: luminous paints for watch dials and instrument panels.
• Medical: limited therapeutic uses in brachytherapy historically; other radionuclides now preferred.
• Scientific: reference sources and research into radioactivity and radiation chemistry.

Isotopes and radiation

Radium has multiple radioactive isotopes, the most common historically being radium-226. All isotopes decay by emitting alpha particles and other radiation; for an overview of isotopic behavior and decay chains see the isotope resources here. The decay products and emitted radiation require careful control and shielding in handling and disposal.

Health risks, regulation and legacy

Prolonged or unprotected exposure to radium can cause serious health problems because of ionizing radiation. Notably, industrial use of radium paint in the early 20th century led to illnesses among factory workers — a widely reported case known as the "radium girls" — which spurred workplace safety reforms and stronger regulation of radioactive materials. Today, many uses once common are banned or limited, and safer alternatives are standard. For legal and occupational safety guidance, consult regulatory summaries and historical cases here and here.

Occurrence and production

Radium is found in trace amounts in uranium and thorium ores and is recovered as a by-product of uranium mining and processing. Because of its radioactivity and scarcity, production is controlled and conducted under strict regulation. For more information on extraction and industrial practice, see the technical overviews atomic data and historical accounts.

Radium occupies an important place in the history of chemistry and medicine: it helped reveal atomic structure and the biological effects of radiation, but it also provided early, powerful lessons about occupational safety and the need for regulation of radioactive materials. For further reading and contemporary safety standards see additional sources here, here, and here.