What determines electronegativity well, it turns out another important principle known as effective nuclear charge determines or creates electronegativity. Now effective nuclear charge is simply the charge that the balanced electrons found in the outermost shell feel due to the protons found in the nucleus. Remember, electrons and protons attract one another. Now, normally, the effective nuclear charge is smaller than the actual nuclear charge found in the nucleus. And that's because some of the electrons found in the innermost shell shield the charge. They decrease the charge, creating a shielding effect.