Delta bond Formation of a δ bond by the overlap of two d orbitals 3D model of a boundary surface of a δ bond in Mo2 In chemistry, a delta bond (δ bond) is a covalent chemical bond, in which four lobes of an atomic orbital on one atom overlap four lobes of an atomic orbital on another atom. This overlap leads to the formation of a bonding molecular orbital with two nodal planes which contain the internuclear axis and go through both atoms. The Greek letterδ in their name refers to d orbitals, since the orbital symmetry of the δ bond is the same as that of the usual (4-lobed) type of d orbital when seen down the bond axis. This type of bonding is observed in atoms that have occupied d orbitals with low enough energy to participate in covalent bonding, for example, in organometallic species of transition metals. Some rhenium, molybdenum, technetium, and chromium compounds contain a quadruple bond, consisting of oneσ bond, twoπ bonds and one δ bond. In the case of the [Re2Cl8]2- ion in the D4h Point group, the bonding delta interaction is the highest energy bonding interaction, followed by the bonding pi, and sigma interactions. The resultant antibonding delta interaction is the lea