In f-block elements two outermost orbitals are​

Hint: The differentiating electron in f-block elements enters the antepenultimate shell's f-orbital. In other words, as electrons fill up, the final electron reaches the shell's f-orbital, which is two shells before the valence shell.

Complete Step by Step Answer:
Inner transition elements are referred to as f block elements. They go by the names lanthanides and actinides as well. The 28 f block elements range in atomic number from 58 to 71 and from 90 to 103. The periodic table classifies them as being in group 3. The final electrons enter the 5f subshell in actinides as opposed to the 4f subshell in lanthanoid.

The outermost shell, the valence shell, is expressed as "n" in a standard electrical arrangement. The penultimate shell is the shell that comes before the valence shell. It is displayed as (n-1). The shell that precedes the penultimate shell is referred to as the anti-penultimate shell and is symbolised as (n-2).

The differentiating electrons in f-block elements enter the f-orbital of the anti-penultimate shell. A further point is that the f-orbital can hold a maximum of 14 electrons. We can also consider the fact that the electronic configurations of all f-block elements conclude with two electrons in the valence shell s-orbital.

In other words, this is how the overall electronic arrangement concludes. The filling up of the 4f and 5f orbitals corresponds to two series in the f block. The elements are in the 4f and 5f series of Ce to Lu and Th to Lw, respectively.

Note: The two rows of elements that are arranged independently at the bottom of the periodic table are referred to as the F-block elements. The lanthanide series is the row that starts with the element lanthanum, and the actinide series is the row that starts with the element actinium.