I dunnu, I googled the same thing. This guys notes says "A group of elements in the first row of the rare earth elementsin the periodic table"
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...
mosley
Yes they are but less than Actinoids.
No, it is not.
Thorium, atom no. 90, just after Actinium (89)