In the f-block elements differentiating electron enters into f-orbital of shell.

Understanding the inner transition elements is crucial as they hold exceptional properties due to their unique electron configuration. The name 'inner transition elements' stems from their placement in the periodic table as well as their electronic structure. Rather than being situated in the main body of the periodic table, these elements are found in two rows at the bottom, separate from the rest.

Essentially, inner transition elements consist of two series: the Lanthanide and Actinide series. What characterizes these elements is the gradual filling of their f-orbitals with electrons as we move across the series. Unlike the more familiar s or p orbitals, f-orbitals have a more complex structure which affects the chemistry and physics of these elements. The fact that their f-orbitals are shielded by other electrons in the 'outer' orbitals gives these elements their 'inner' label.

Delve into the electron configuration of inner transition elements, it's essential to grasp how the differentiating electron defines each element's chemical and physical properties. In general, electron configuration refers to the distribution of electrons in an atom's orbitals. Each element has a unique electron configuration that explains much about its behavior and position in the periodic table.

When it comes to f-block elements, their distinctive electron configuration includes the f-orbitals, which are not filled in a simple, straightforward way like s or p orbitals. The f-orbitals can house up to 14 electrons, and these occupy a space that is 'inner', or deeper within the atom, compared to other orbitals. The specific electron configuration for any f-block element indicates where its differentiating electron is placed, which is central to the formation of its electronic structure and thus its unique properties.

The Lanthanide and Actinide series represent the two rows of the f-block and showcase distinctive properties because of their differing electron configurations. Each series corresponds to the filling of the 4f and 5f orbitals, respectively.

The Lanthanide series includes elements with atomic numbers from 57 to 71 and is known for members with high magnetic susceptibility and specific optical properties due to the electrons in the 4f orbitals. These elements are often dubbed as 'rare earth metals' and are widely used in electronics, magnets, and various high-tech applications.

Conversely, the Actinide series encompasses elements from atomic number 89 to 103. These are noted for their radioactive properties, with many of these elements being synthetic and highly unstable. Their electron configuration involves the filling of 5f orbitals, which considerably affects their chemical reactivity and also makes them suitable for use in nuclear energy and weaponry.

It's interesting to note that the properties of the elements in both series become less predictable as the 4f and 5f orbitals fill, due to their complex interactions and the shielding effect from the outer electrons.