f-block

The f-block brings together the 15 lanthanides (period 6, La–Lu) and the 15 actinides (period 7, Ac–Lr), where the (n−2)f subshell is being filled. These elements exhibit very similar chemical properties (especially the lanthanides) because the deeply buried f subshell has little influence on the valence chemistry. Lanthanides are essential to permanent magnets, luminescent displays and catalysts; actinides are all radioactive, dominated by uranium and plutonium. By visual convention, the f-block is detached from the main body of the table to keep it from becoming excessively wide.