In f-block elements, the electrons enter in which of the following shell?

Penultimate shell Antipenultimate shell (n-2)f subshell Both (2) and (3)

Antipenultimate shell

The elements in which their elemental or ionic forms have partly filled f-orbitals are termed as f-block elements. These are known as inner transition elements. These are so called because electrons in these elements enters into antipenultimate shell.