Because the number of bounced electrons found in each atom increases as we go from left to right on our periodic table. Also the ratio of bounce electrons to the innermost electrons also increases. So let's take lithium, for example, and let's compare it to fluorine. So Lithium has one bounced electron in the two S shell, while this fluorine has seven bounced electrons. So because this has more balanced electrons and because the ratio is seven to two versus one to two, because the ratio here is much larger, this has much more effective nuclear charge and therefore it's more electronegative. So electronegativity in polar bonds go hand in hand.