A common property of aromatic molecules is their ability to absorb electromagnetic radiation in the near ultraviolet or even in the visible range, thereby making the molecules brightly colored. The effect of combining p orbitals in benzene into a set of delocalized MO's is to split the energy of the individual p orbitals into four closely spaced energy levels, which were diagramed previously. In benzene, the three bonding orbitals are filled and the antibonding orbitals are empty. If the right frequency of radiation is supplied, a benzene molecule can absorb it and promote one or more electrons from bonding to antibonding orbitals. The gap between levels is a measure of the energy needed to make the transition from the ground state (lowest energy) to an excited electronic state. An excited molecule can emit this energy later as a photon of radiation, and drop back to the ground state. Nonaromatic molecules also can be electronically excited, but larger amounts of energy are required, and this means that absorption and emission take place farther into the ultraviolet. If enough energy is supplied, the s- single bonds can be broken and the molecules destroyed. The special property of aromatic molecules is that their p- orbital energy levels are closely spaced , which leads to absorption in the lower-energy, longer-wavelength region.