Polar and Nonpolar Bonds

Polar - can be formed by two atoms of different elements

        Water has two polar O-H bonds in a bent geometry

If the bond dipole moments of the molecule do not cancel, the molecule is polar. For example, the water molecule (H₂O) contains two polar O-H bonds in abent (nonlinear) geometry. The bond dipole moments which do not cancel, so that the molecule forms a molecular dipole with its negative pole at the oxygen and its positive pole midway between the two hydrogen atoms. In the figure each bond joins the central O atom with a negative charge (red) to an H atom with a positive charge (blue).

• Non-polar bonds occur when the difference in electronegativity between the two atoms is less than 0.4
• Polar bonds occur when the difference in electronegativity between the two atoms is between 0.4 and 2.0
• Ionic bonds occur when the difference in electronegativity between the two atoms is greater than 2.0

Nonpolar- two atoms of similar element 

               -electron are electrically uniform

                -sysmetrical structure

               

  

• A bond between 2 nonmetal atoms that have the same electronegativity and therefore have equal sharing of the bonding electron pair
• Example: In H-H each H atom has an electronegativity value of 2.1, therefore the covalent bond between them is considered nonpolar.

Electronegativity- the ability of an atom to attract additional electron towards itself. The value can be found in the periodic table. 

*However,there are substances with polar bonds but are considered as nonpolar molecule,due to cancellation of dipoles ( opposite directions )

Molecular Dipole

• A result of the bond dipoles in a molecule.
• Bond dipoles may or may not cancel out thereby producing either molecules that are nonpolar, if they cancel, or polar, if they do not cancel
• Examples:
• CO₂ is a linear molecule with 2  bond dipoles that are equal and oppositely directed therefore the bond polarities cancel and the molecule is nonpolar.