4dz2 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 4dz2 orbital has a unique shape resembling consists of six lobes elongated along the z-axis with a doughnut-shaped region (or torus) around the nucleus on the x-y plane. The orbital is seen transparent at middle to show the axes of symmetry and the conical nodes and radial 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 4dz2 electron orbital, 4 indicates that it is the fourth energy level, d indicates that the orbital is specifically a d-orbital, and (z2) indicates that the lobes of the orbital are oriented along the z-axis. The 4dz2 orbital can accommodate up to 2 electrons. It is part of the 4d shell, which contains five orbitals in total. The 4d orbitals are part of the 4 shell, which also contains one spherical 4s orbital and three bi-lobed 4p orbitals, both at a lower energy, and seven lobed 4f orbitals at a higher energy level (not seen).