Why are f-block elements called inner transition metals?

The f-block elements (lanthanides and actinides) are called inner transition metals because:

1. Position of filling – In these elements, the extra electrons go into the inner f-orbitals (4f in lanthanides, 5f in actinides) instead of the outer shells. That means the “transition” is happening deep inside the atom, not just in the outer layers.
2. Placed inside the periodic table – They actually belong to period 6 and 7 of the table, but are usually shown separately at the bottom. If placed properly, they would fit inside the main body of the transition metals (between group 3 and group 4).
3. Similar properties to transition metals – Like d-block transition metals, they:
   • Show variable oxidation states
   • Form colored ions
   • Often show magnetic properties
   • Can act as catalysts

But since the electrons are filling the inner f-orbitals, not the d-orbitals, they are called inner transition metals.

In short:
They are called inner transition metals because their f-orbitals (inner shells) are being filled, while they behave like transition metals in many ways.