Discovery of actinium

Actinium was discovered in 1899 by the French chemist Andre-Louis Debierne, a friend and collaborator of Marie and Pierre Curie, who found it in the residue of pitchblende after the removal of uranium and radium. The German chemist Friedrich Giesel found the same element independently a few years later, in 1902. The name comes from the Greek aktis, meaning ray, because the element is strongly radioactive. Actinium is a rare, silvery metal and the first member of a group of elements called the actinides. It occurs in tiny amounts in uranium ores, and most of what is used in research is now made in nuclear reactors. It glows with a pale blue light in the dark, and is hundreds of times as radioactive as radium.

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