where the dissociation energies (that is, the energy needed to break the bond between the atoms), "E", of A-B, A-A and B-B bonds are given in electronvolts, and the factor (eV) is added to make sure the final answer has no unit. With the above formula, we can calculate the difference in elecronegativity between hydrogen and bromine to be 0.73. (dissociation energies: H-Br, 3.79 eV; H-H, 4.52 eV; Br-Br, 2.00 eV)