5z(x2-y2) electron orbital, illustration. 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 5fz(x2-y2) orbital is made up of sixteen lobes. The orbital is seen transparent at middle to show the axes of symmetry and the three planar nodes and spherical node can be seen at right. Nodes are the regions in an atom with zero electron density and where the electron is least likely to exist. For the 5fz(x2-y2) electron orbital, 5 indicates that it is the fifth energy level, f indicates that the orbital is specifically an f-orbital, and z(x2-y2) indicates a complex orientation in the x-, y-, and z-planes. The f-orbitals are more complex in shape compared to s-, p-, and d-orbitals, and they have a total of seven possible orientations. The 5fz(x2-y2) orbital can accommodate up to 2 electrons. The 5f orbitals are part of the 5 shell, which also contains one spherical 5s orbital, three bi-lobed 5p orbitals, and five daisy-shaped 5d orbitals (except z2) all at a lower energy level (not seen).