Describing elements that tend to gain electrons and form negative ions. The halogens are typical electronegative elements. For example, in hydrogen chloride, the chlorine atom is more electronegative than the hydrogen and the molecule is polar, with negative charge on the chlorine atom. There are various ways of assigning values for the electronegativity of an element. Mulliken electronegativities are calculated from E = (I + A)/2, where I is ionization potential and A is electron affinity. More commonly, Pauling electronegativities are used. These are based on bond dissociation energies using a scale in which fluorine, the most electronegative element, has a value 4. Some other values on this scale are B 2, C 2.5, N 3.0, O 3.5, Si 1.8, P 2.1, S 2.5, Cl 3.0, Br 2.8. A simple definition of electronegativity is the average one-electron energy of the valence electrons in the ground state of free atoms.