What is the term for the group that includes the lanthanide and actinide series?

The group that includes both the lanthanide and actinide series is known as the inner transition metals. This classification is based on their position in the periodic table, specifically in the f-block, where these elements are located.

Lanthanides (elements 57-71, from lanthanum to lutetium) and actinides (elements 89-103, from actinium to lawrencium) are characterized by the filling of f orbitals. This distinguishes them from other metals in the periodic table, such as transition metals, which fill d orbitals.

The term "inner transition metals" reflects their unique placement beneath the main body of the periodic table, indicating that they are indeed transition metals, but they belong to a separate category due to their distinct electronic configurations and properties.

Understanding this classification helps in comprehending the overall structure of the periodic table and the relationships between different groups of elements, particularly when examining their chemical properties and behaviors.