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Lesson 28 Bonding

Bonds & Electronegativity


TYPES OF BONDS

• 3 main types of bonds 

1. Ionic ( metal - nonmetal )
        ~ e- are transferred from metal to non-metal
2. Covalent (nonmetal to nonmetal)
        ~ e- are shared between non-metals
3. Metallic (metal)              
        ~ holds pure metals together by electrostatic attraction

Electronegativity

• Electronegativity (en) is a measure of an atom's attraction for electrons in a bond 

               Fluorine = 4.0
               Chlorine = 3.0
               Cesium = 0.8

• Atoms with greater en attract e- more 
• Polar covalent bonds form from an unequal sharing of e- 
• Non-polar covalent bonds form from equal sharing 

Bonds 

• The type of bond formed can be produced by looking at the difference in electronegativity (en) of the elements 

                 en  > 1.7 = ionic bond
                 en  < 1.7 = polar covalent bond
                 en  =  0  is non-polar covalent bond

Example 1
Predict the type of bond ' formed' 
C - C 
2.55 - 2.55 = 0          non-polar covalent bond! 


Pb - B 
2.33 - 2.04 = 0.29     polar covalent bond! 


Ba - F
0.89 - 3.99  =  3.1     ionic bond! 


Identify the positive and negative side of the polar bonds 
B - Cl 
2.04 - 3.18 = 1.14     polar covalent bond!    
B+       Cl-


C - N 
2.55 - 3.04 =  0.49   polar covalent bond!
C+        N-


- kim 

posted by chemistry11 @ 6:38 PM