Electronegativity
where the dissociation energies (that is, the energy needed to break the bond between the atoms), Ed, of A-B, A-A and B-B bonds are given in electronvolts, and the factor (eV)-½ 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)