Actinium
Actinium is a silvery radioactive metallic element. Actinium glows in the dark due to its intense radioactivity with a blue light. Actinium was discovered in 1899 by André-Louis Debierne, a French chemist, who separated it from pitchblende. Friedrich Otto Giesel independently discovered actinium in 1902. The chemical behavior of actinium is similar to that of the rare earth lanthanum. The word actinium comes from the Greek aktis, aktinos, meaning beam or ray.