What are all of the elements that end with f electrons

The elements whose electron configurations end with f electrons are in the Lanthanide and Actinide series: those long series at the bottom of the Periodic Table (see image).

The atoms are adding electrons into f orbitals, but the f electrons are not always the last electrons in the electron configuration.

For example, the electron configuration of Eu is [Xe]6s²4f⁷, but that of Gd

is [Xe] 6s²4f⁷5d.

I have blocked off in red all the exceptions like Gd.

explanation:

i think option no d is the correct answer

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."