4fz3 electron orbital, computer model. An electron orbital is a region around an atomic nucleus (not seen) in which one or a pair of electrons is most likely to exist. The pink area is where an electron has a positive wave function, and the orange area is where the wave function is negative. The 4fz3 (or 4fzzz) orbital is part of the 4f shell, which contains seven orbitals in total. The 4f shell is partially full in the Lanthanide metals.
