Actinium

Actinium (pronounced /ækˈtɪniəm/, ak-TIN-nee-əm) is a radioactive chemical element with the symbol Ac and atomic number 89, which was discovered in 1899. It was the first non-primordial radioactive element to be isolated. Polonium, radium and radon were observed before actinium, but they were not isolated until 1902. Actinium gave the name to the actinoid series, a group of 15 similar elements between actinium and lawrencium in the periodic table... more

Actinium (pronounced /ækˈtɪniəm/, ak-TIN-nee-əm) is a radioactive chemical element with the symbol Ac and atomic number 89, which was discovered in 1899. It was the first non-primordial radioactive element to be isolated. Polonium, radium and radon were observed before actinium, but they were not isolated until 1902. Actinium gave the name to the actinoid series, a group of 15 similar elements between actinium and lawrencium in the periodic table. André-Louis Debierne, a French chemist, announced the discovery of a new element in 1899. He separated it from pitchblende and described the substance (in 1899) as similar to titanium and (in 1900) as similar to thorium. Friedrich Oskar Giesel independently discovered actinium in 1902 as a substance being similar to lanthanum and called it "emanium" in 1904. After a comparison of substances in 1904, Debierne's name was retained because it had seniority. The history of the discovery stayed questionable and in publications from 1971 and later... less