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. In fact, polar bonds or polar codalent bonds are formed because of differences in electronegativity. Once again, polar bonds are created due to electronegativity differences between the atoms composing the bond. So, as an example, let's look at HF.