The lanthanides and actinides are located in which block of the periodic table?

The periodic table is divided into blocks based on which electron shell fills up in each element. Lanthanides and actinides fill their f-orbitals, so they belong to the f-block.

These two rows of elements are usually shown separately at the bottom of the periodic table to save space. They include rare earth metals and radioactive elements.

The f-block contains 28 elements total: 14 lanthanides and 14 actinides. These elements have similar chemical properties because they all fill f-orbitals with electrons.