Term: actinium (Ac)
Literally meaning: “pertaining to ray”
'áκτίς actis(genitive áκτ[éνος/actinos)(=ray, beam)
The element was named after its power of emitting energy in the form of rays suchas radioactive “radium” which comes from latin radius=ray.
Actinium was found in 1899 by French chemist Andre-Louis Dabierne (1874-1949) and by German chemist Friedrich Oskar Giesel (1852-1927) in 1902 independently. Giesel named it “emanium” but finally it was chosen Dabierne name because of its seniority. Dabierne who worked with Marie Curie discovered actinium in an uranium ore from which radium and polonium had been isolated.
Actinium is a soft silvery-white and highly radioactive chemical element with atomic number 89 and atomic mass 229. Actinium has 29 radioactive isotopes and glows in the dark. Because of its high radioactivity the lelement is used as neutron sourse.