Chemical Element: actinium

(Modern Latin: chemical element; from Greek, aktis, aktinos ray; radioactive metal)

Chemical-Element Information

Symbol: Ac
Atomic number: 89
Year discovered: 1899

Discovered by: French chemist André-Louis Debierne (1874-1949), and independently by F. O. Giesel, in 1902, both of whom obtained it while working on “separation techniques” for rare earth oxides.

  • There was more in uranium ores than the polonium and radium that the Curies had detected (see polonium).
  • Debierne, a close friend of the Curies, isolated still another element from the ores which he called “actinium”, from a Greek word for “ray”, so that the name was the Greek equivalent of the Latin “radium.”
  • In the past, actinium was of interest only as a scientific study; however, it is now being considered as a source of heat in space vehicles.
  • actinometer, the general name for any instrument used to measure the intensity of radiant energy.
  • actinomycosis, an infectious disease caused by Gram-positive bacteria with a characteristic filamentous branching shape which are known as actinomycetes.

Name in other languages:

French: actinium

German: Actinium

Italian: attinio

Spanish: actinio

Information about other elements may be seen at this Chemical Elements List.

A special unit about a variety of words that include chemo-, chem- may be seen here.