Actinium

Uraninite-39029

DOTA polyaminocarboxylic acid

Actinium is a chemical element with the symbol Ac and atomic number 89. Actinium gave the name to the actinide series, a group of 15 similar elements between actinium and lawrencium in the periodic table. It is also considered the first of the 7th-period transition metals. Discovered in 1899 by Friedrich Oskar Giesel, actinium was the first non-primordial radioactive element to be isolated. Marie Curie and André-Louis Debierne are also credited with discovering the element independently.

Properties

Actinium is a soft, silvery-white, radioactive, metallic element. Its physical and chemical properties most closely resemble those of lanthanum, the element above it in the periodic table. Actinium glows in the dark with a pale blue light, which results from its intense radioactivity. It has a melting point of approximately 1050 °C and a boiling point of 3200 °C. Being radioactive, actinium has no significant commercial applications, but it is used in research and as a source of neutrons.

Isotopes

Actinium has no stable isotopes. The most stable isotope, Actinium-227, has a half-life of 21.77 years and is a byproduct of the decay of uranium-235. It is used in the production of radium-223, a radioisotope used in the treatment of cancer. Other isotopes of actinium are of scientific interest but have limited applications due to their short half-lives and intense radioactivity.

Occurrence and Production

Actinium is extremely rare, occurring naturally in trace amounts in uranium and thorium ores. The most common source of actinium is the decay of uranium-235. It can be isolated from these ores, but the process is complex and not commercially viable due to its scarcity and radioactivity. Synthetic actinium is produced in nuclear reactors by irradiating radium-226 with neutrons.

Applications

Due to its strong radioactivity, actinium's applications are limited and mostly confined to research. Actinium-227 is used as a neutron source and in radiation therapy for treating cancer. It is also used in the study of the properties of actinides and in the development of new materials.

Safety

Actinium is highly radioactive and must be handled with care. Exposure to actinium can cause radiation sickness, and adequate safety measures must be taken when handling it, including the use of protective clothing and proper containment.

See Also

• Actinide series
• Radioactivity
• Neutron source
• Radiation therapy