Bonds and Electronegativity

There are three main types of bonds, two of which we already learned in grade 10.

• Ionic (Metal-Nonmetal)
• Covalent (Nonmetal-Nonmetal)
• Metallic (Metal-Metal)

In Ionic bonds, electrons(e-) are transferred whereas in Covalent bond, e- are shared between the two atoms. Metallic bonds involve two metals which are held together by electrostatic attraction.

Next we have to talk about electronegativity (EN). EN is a measure of an atoms attraction for e- in a bond. EN ranges from 4 to 0.7 and follows a specific trend on the periodic table.

                                  EN > 1.7    =  Ionic Bond
                                  EN < 1.7    = Polar Covalent Bond
                                  EN = 0       = Nonpolar Covalent Bond


Lets try some examples: 

Ex1.      Ca-P
            1.0-2.19
            1.19 = Polar Covalent Bond

 http://www.youtube.com/watch?v=Kj3o0XvhVqQ





So atoms with greater EN attract more e-s, forming two different kinds of covalent bonds: polar and nonpolar. Polar covalent bonds have an unequal sharing of electrons while nonpolar covlent bonds share electrons equally.

The different types of bonds can be predicted based on the difference of EN of the two atoms:

                                  EN > 1.7    =  Ionic Bond
                                  EN < 1.7    = Polar Covalent Bond
                                  EN = 0       = Nonpolar Covalent Bond


Lets try some examples: 

Ex1.      Ca-P
            1.0-2.19
            1.19 = Polar Covalent Bond

Ex2.       K-Br
              0.82-2.96
              2.14 = Nonpolar Covalent Bond

Ex3.       Cl-Cl
              3.18-3.18
              0 = Ionic Bond