2s 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 orbital is seen halved at right to show the spherical node contained within it. The blue area is where the wave function of the electron has a positive value, and the gold area is where it is negative. The 2 shell contains this 2s orbital and three 2p orbitals (not seen) at a slightly higher energy level.