Actinium (Ac)
Overview of Actinium
Actinium is a soft, silvery-white, highly radioactive metal. One of its striking features is a faint blue glow, caused by its intense radioactivity exciting the air around it.
It was the first element discovered in the actinide series of the periodic table. The name comes from the Greek aktinos, meaning “ray” or “beam,” reflecting its radioactive nature.
Uses of Actinium
Actinium is not used in consumer products because of its scarcity and radioactivity, but it is valuable in scientific research and medicine.
Alpha particle source: Actinium is an intense emitter of alpha radiation, making it useful for studies in nuclear physics.
Targeted cancer therapy: The isotope actinium-225 is being investigated for targeted alpha therapy (TAT). When linked to molecules that seek out cancer cells, it can deliver concentrated radiation to tumors while minimizing harm to healthy tissue.
Natural abundance and production
Actinium is extremely rare in nature. It occurs in trace amounts within uranium ores, most commonly as actinium-227, which has a half-life of 21.7 years and forms during the decay of uranium-235. A tonne of pitchblende ore contains only about 150 milligrams of actinium.
For research purposes, actinium is usually produced artificially by bombarding radium-226 with neutrons in a nuclear reactor.
Discovery and history
Actinium’s discovery involved two chemists:
André-Louis Debierne (1899): Working with Marie and Pierre Curie, Debierne first reported the new element, which he extracted from pitchblende.
Friedrich Otto Giesel (1902): Independently isolated the same element and called it emanium, unaware of Debierne’s earlier announcement.
Although Giesel provided a clearer description of the element’s properties, official credit for the discovery goes to Debierne.