Actinide

The actinoid (IUPAC nomenclature) or actinide (traditional nomenclature still in wide use) series encompasses the 15 chemical elements that lie between (and inclusive of) actinium and lawrencium included on the periodic table, with atomic numbers 89 - 103. The actinoid series derives its name from the first element in the series, actinium, and ultimately from the Greek ακτις (aktis), "ray," reflecting the elements' radioactivity. The actinoid ser... more

The actinoid (IUPAC nomenclature) or actinide (traditional nomenclature still in wide use) series encompasses the 15 chemical elements that lie between (and inclusive of) actinium and lawrencium included on the periodic table, with atomic numbers 89 - 103. The actinoid series derives its name from the first element in the series, actinium, and ultimately from the Greek ακτις (aktis), "ray," reflecting the elements' radioactivity. The actinoid series (An) is included in some definitions of the rare earth elements. IUPAC is currently recommending the name actinoid rather than actinide. The suffix -ide can indicate one of a group of related compounds (azide, polysaccharide), a binary compound of a nonmetal (bromide, arsenide) or one of a group of several elements (lanthanide, actinide), while -oid means "similar to"). There are alternative arrangements of the periodic table that exclude actinium or lawrencium from appearing together with the other actinoids. The actinoids display less... less