Question

what is the first noble gas with electrons occupying 4f orbitals? Please help ?!!

Answer 1

Radon (atomic number 86) is your answer. The next lower noble gas, xenon, has no
electrons in the 4f level, although the 4s, 4p, and 4d levels are full. The 4f level begins
to fill at atomic number 58 (cerium) and it is full when you get to radon, with an
atomic number of 86.