Polarity And Covalent Bonding

Non-polar covalent bonds form when electrons in the molecular orbital are shared equally among the atoms in the bond, this usually occurs when the atoms being bonded are the same. If the atoms have significantly different electronegativity values, the electrons are shared unequally between atoms in the molecular orbital. When this happens, the bond formed is a polar covalent bond. In this bond, the shared electrons in the molecular orbital are more likely to be found close to the atom with the higher electonegativity. However, if the elctronegativity values of the atoms vary greatly, an electron will be removed from the electron with lower electronegativity and the atoms will be bonded ionically. Polar covalent bonds are called polar because the ends of them are opposites. In these polar molecules, the atom that attracts the most electrons has a partial negative charge (symbolized by δ-) while the other atom has a partial positive charge (symbolized by δ+). When a molecule has one end partially positively charges and the other end partially negatively charged, it is called a dipole. Even though positive and negative charges are present, the bond is not ionic, as an electron is not removed from one atom and transferred to the other. The electrons are still shared, but the shared pair is more likely to be found near the atom with the highest electronegativity. This makes the charge unequal and the bond is therefore polar covalent. The greater the polarity of a bond, the greater the electronegativity difference will be. The greater electronegativity differs between atoms, the stronger the bond will be.