The f-block of the periodic table of elements consists of those elements (sometimes referred to as the inner transition elements) for which, in the atomic ground state, the highest-energy electrons occupy f-orbitals. Unlike the other blocks, the conventional divisions of the f-block follow periods of similar atomic number rather than groups of similar electron configuration. Thus, the f-block is divided into the lanthanide series and the actinide series.

The name 'inner transition' is derived by analogy with the transition metals.

Related topics

• Periodic table block
  • s-block
  • p-block
  • d-block
  • g-block
• Electron configuration