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.

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