any of the elements in the series () of radioactive, metallic chemical elements from element 89 (actinium) through element 103 (lawrencium): actinides resemble lanthanides in electronic structure
Origin of actinide; from 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.