0Certain covalent bonds have a property called Polarity. Two atoms joined by a covalent bond share electrons, their nuclei are held by the same electron cloud. But in most cases the two nuclei do not share the electrons equally, the electron cloud is denser about one atom than the other. One end of the bond is relatively negative and the other end is relatively positive, thus there will be a negative pole and a positive pole. Such a bond is said to be a polar bond or to possess polarity. Bond polarities are intimately concerned with both physical and chemical properties. The poalrity of bonds can lead to polarity of molecules and thus profoundly affect melting point, boiling point and solubility. The polarity of a bond determines the kind of reaction that can take place at that bond, and even affects reactivity at near by bond.
