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. So h donates one electron and the fluorine also donates one electron. But because this fluorine atom is more electronegative, it attracts electrons more strongly. That means that electron density will be closer.