3d(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 3d(x2-y2) orbital made up of four lobes, centred on the nucleus. The orbital is seen transparent at middle to show the axes of symmetry and the planar 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 3d(x2-y2) electron orbital, 3 indicates that it is the third energy level, and d indicates that the orbital is shaped like a four leaf clover (with the exception of the the dz2 orbital), and (x2-y2) indicates the orientation of the orbital is in the xy-plane. The 3d(x2-y2) orbital can accommodate up to 2 electrons. It is part of the 3d shell, which contains five orbitals in total. The 3d orbitals are part of the 3 shell, which also contains one spherical 3s orbital and three bi-lobed 3p orbitals, both at a lower energy (not seen).