<P> In the simple aromatic ring of benzene the delocalization of six π electrons over the C ring is often graphically indicated by a circle . The fact that the six C-C bonds are equidistant is one indication that the π electrons are delocalized; if the structure were to have isloated double bonds alternating with discrete single bonds, the bond would likewise have alternating longer and shorter lengths . In valence bond theory, delocalization in benzene is represented by resonance structures . </P> <P> Delocalized electrons also exist in the structure of solid metals . Metallic structure consists of aligned positive ions (cations) in a "sea" of delocalized electrons . This means that the electrons are free to move throughout the structure, and gives rise to properties such as conductivity . </P> <P> In diamond all four outer electrons of each carbon atom are' localized' between the atoms in covalent bonding . The movement of electrons is restricted and diamond does not conduct an electric current . In graphite, each carbon atom uses only 3 of its 4 outer energy level electrons in covalently bonding to three other carbon atoms in a plane . Each carbon atom contributes one electron to a delocalized system of electrons that is also a part of the chemical bonding . The delocalized electrons are free to move throughout the plane . For this reason, graphite conducts electricity along the planes of carbon atoms, but does not conduct in a direction at right angles to the plane . </P> <P> Standard ab initio quantum chemistry methods lead to delocalized orbitals that, in general, extend over an entire molecule and have the symmetry of the molecule . Localized orbitals may then be found as linear combinations of the delocalized orbitals, given by an appropriate unitary transformation . </P>

What does it mean for a lone pair to be delocalized