Electronegativity refers to the measure of the tendency of an atom to attract a bonding pair of electron. Electronegativity values range between 0.7 and 4.0; 4.0 for flourine, which is the most electronegative element and 0.7 for cesium and francium that are the least electronegative, all the other elements falls in between. In polar molecules, elements with different value of electronegativity are sharing pairs of electrons; the more electronegative element will pull the shared bonding pair of electrons closer to itself than the one who has less value of electronegativity, this will results in unequal sharing of the shared electron pairs.