any of the elements in the series (actinide series) of radioactive, metallic chemical elements from element 89 (actinium) through element 103 (lawrencium): actinides resemble lanthanides in electronic structure
Origin of actinidefrom actin(ium) + -ide
Any of a series of chemically similar, radioactive elements with atomic numbers ranging from 89 (actinium) through 103 (lawrencium). Also called actinoid .
Origin of actinideactin(ium) -ide
actin- + -ide