Chapter 5
Compounds and Their Bonds
5.7
Electronegativity and Bond Polarity

General, Organic, and Biological Chemistry

Copyright © 2010 Pearson Education, Inc.

1

Electronegativity
The electronegativity value
 indicates the attraction of an atom for shared electrons  increases from left to right going across a period on the periodic table
 decreases going down a group on the periodic table  is high for the nonmetals, with fluorine as the highest  is low for the metals
General, Organic, and Biological Chemistry

Copyright © 2010 Pearson Education, Inc.

2

Some Electronegativity Values
High
values

Low values General, Organic, and Biological Chemistry

Copyright © 2010 Pearson Education, Inc.

3

Nonpolar Covalent Bonds
A nonpolar covalent bond
 occurs between nonmetals
 has an equal or almost equal sharing of electrons
 has almost no electronegativity difference (0.0 to 0.4)
Examples:
Atoms
Electronegativity Type of Bond
Difference
_______________
N–N
3.0 – 3.0 = 0.0
Nonpolar covalent
Cl–Br
3.0 – 2.8 = 0.2
Nonpolar covalent
H–Si
2.1 – 1.8 = 0.3
Nonpolar covalent
General, Organic, and Biological Chemistry

Copyright © 2010 Pearson Education, Inc.

4

Polar Covalent Bonds
A polar covalent bond
 occurs between nonmetal atoms
 has an unequal sharing of electrons
 has a moderate electronegativity difference
(0.5 to 1.7)
Examples:
Atoms
Electronegativity Type of Bond
Difference
__________ _
O–Cl
3.5 – 3.0 = 0.5
Polar covalent
Cl–C
3.0 – 2.5 = 0.5
Polar covalent
O–S
3.5 – 2.5 = 1.0
Polar covalent
General, Organic, and Biological Chemistry

Copyright © 2010 Pearson Education, Inc.

5

Comparing Nonpolar and Polar
Covalent Bonds

General, Organic, and Biological Chemistry

Copyright © 2010 Pearson Education, Inc.

6

Ionic Bonds
An ionic bond
 occurs between metal and nonmetal ions
 is a result of electron transfer
 has a large electronegativity difference (1.8 or more).
Examples:
Atoms
Electronegativity
Type of Bond
Difference