3d electron orbitals, 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. Four of the five 3d orbitals are made up of four lobes, centred on the nucleus. The orbital at top is bilobed with an encircling ring. They are part of the 3 shell, which also contains one spherical 3s orbital and three bi lobed 3d orbitals, both at a lower energy (not seen). The 3d shells are partially full in the first row of transition metals. These metals typically form coloured compounds as electron transitions between 3d orbitals absorb some visible wavelengths of light.