The lanthanide series are the rare earth elements are the chemical elements which lie between lanthanum and ytterbium on the periodic table. That is, they have atomic numbers between 57 and 70 inclusive. Below them are the actinides.
Lanthanides are elements in which the f orbitals is partly or completely filled, while the outermost p and d orbitals are empty. Since the f orbitals do not have as much effect on chemistry as the s, p, and d, they are chemically similar to each other.
The lanthanides are typically placed below the main body of the periodic table, in the manner of a footnote. The full-width version of the periodic table shows the position of the lanthanides more clearly.