6d(x2-y2) 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 6d(x2-y2) orbital made up of sixteen lobes, centred on the nucleus. The orbital is seen transparent at middle to show the axes of symmetry and the planar nodes and spherical nodes 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 6d(x2-y2) electron orbital, 6 indicates that it is the sixth energy level, and d indicates that the orbital is shaped like a four leaf clover (except the dz2 orbital), and (x2-y2) indicates the orientation of the orbital is in the xy-plane. The 6d(x2-y2) orbital can accommodate up to 2 electrons. It is part of the 6d shell, which contains five orbitals in total. The 6d orbitals are part of the 6 shell, which also contains one spherical 6s orbital and three bi-lobed 6p orbitals, both at a lower energy, and seven lobed 6f orbitals at a higher energy level (not seen).