What Is Radium?
QUICK ANSWER
Radium is a chemical element with atomic number 88 and the symbol Ra. It's a highly radioactive, silvery-white alkaline earth metal that was once used in luminous paint for watch dials, clocks, and aircraft instruments. Discovered by Marie and Pierre Curie in 1898, radium is now mostly limited to specialized medical applications.
Radium has one of the strangest histories of any element. After Marie Curie's 1898 discovery, radium was hailed as a miracle substance, added to watch dials, toothpaste, water, and quack medicines for decades. By the 1930s, the deadly consequences had become impossible to ignore, especially through the tragic deaths of factory workers known as the Radium Girls. Today, radium has very limited uses but remains a key example of radiation dangers.
Where is radium on the periodic table?
Radium has atomic number 88, the symbol Ra, and sits in group 2 of the periodic table among the alkaline earth metals, alongside calcium, strontium, and barium. All radium isotopes are radioactive, with Ra-226 being the most common, having a half-life of 1,600 years. The element was discovered in 1898 by Marie and Pierre Curie, who isolated about 0.1 gram of radium chloride from several tons of pitchblende ore over a four-year extraction process. Radium occurs naturally as a decay product of uranium and is found in trace amounts throughout Earth's crust.
What are the properties of radium?
Radium is a silvery-white metal that tarnishes black on exposure to air. It melts at 700°C and has a density of 5.5 g/cm³. The element is highly radioactive, releasing alpha, beta, and gamma radiation as it decays. Radium and its decay products give off enough energy to glow visibly blue in the dark, an effect called radioluminescence that fascinated early researchers. The element is chemically similar to barium but far more dangerous. Pure radium reacts vigorously with water and air, and even tiny samples generate significant heat from radioactive decay.
What was the Radium Girls tragedy?
From the 1910s through 1930s, factories employed thousands of young women to paint watch dials, clock faces, and aircraft instruments with luminous radium-containing paint. Workers were instructed to point their brushes by licking them, ingesting small amounts of radium with every dial painted. The radium accumulated in their bones, causing severe radiation damage, anemia, bone cancers, and grotesque jaw deterioration. Many workers died, and their lawsuits established important labor safety laws. The Radium Girls case is now studied as a landmark in occupational health and workers' rights.
What is radium used for today?
Radium's medical uses have been mostly replaced by safer or more effective alternatives, though some applications remain. Radium-223 chloride (Xofigo) treats certain bone metastases from prostate cancer, taking advantage of radium's tendency to concentrate in bone. Some industrial radiography still uses radium sources, though cobalt-60 and other isotopes are more common. The luminous paint applications were largely phased out by the 1960s, replaced first by promethium-based paint and then by tritium and phosphor designs that don't expose workers to dangerous radiation.
Radium went from miracle discovery to industrial tragedy to specialized cancer treatment in just over a century. The same element that killed dial-painting factory workers in the 1920s now extends some cancer patients' lives in the 2020s. Few elements have such a dramatic arc of human use and misuse.
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