The charge-shift bond has been proposed as a new class of chemical bond that SITS alongside the two familiar families of covalentand ionic bonds where electrons are shared or transferred respectively.[1][2] The charge shift bond derives its stability from the resonance of ionic forms rather than the covalent sharing of electrons which are often depicted as having electron density between the bonded atoms. A feature of the charge shift bond is that the predicted electron density between the bonded atoms is low. It has LONG been known from experiment that the accumulation of electronic charge between the bonded atoms is not necessarily a feature of covalent bonds.[3] An example where charge shift bonding has been used to EXPLAIN the low electron density found experimentally is in the central bond between the INVERTED tetrahedralcarbons in [1.1.1]propellanes. Theoretical calculations on a range of molecules have indicated that a charge shift bond is present, a striking example being fluorine, F2, which is normally described as having a typical covalent bond