Elements with 89 or more protons in their nucleus that behave chemically like actinium. All are radioactive and many are long- lived alpha-emitters.

elements in the periodic table with atomic numbers from 90 to 103 (thorium to lawrencium); i.e., elements with a higher atomic number than actinium, which has an atomic number of 89. These are also ca [..]

Actinides are a distinct transition group between actinium and lawrencium (inclusive). The group includes actinium, thorium , protactinium , uranium , neptunium , plutonium , americium , curium , cali [..]

This is a group of elements within the periodic table and are also known as the transuranics. The name refers to those elements with increasing atomic no. from actinium, which all have similar chemica [..]

A series of Radioactive Elements from Actinium, atomic number 89, to and including Lawrencium, atomic number 103.

Those elements with atomic numbers 89 to 103, corresponding to the lanthanides in the Periodic Table. Synonyms: actinide elements. Origin: actinium, first element of the series (05 Mar 2000)