1. Bond Character and Molecular Polarity
How does atom electronegativity affect bond character and molecular polarity?
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Publishing as Benjamin Cummings

2. Electronegativity The electronegativity value
measures an atom’s tendency to attract electrons from other atoms
is higher for nonmetals than for metals
Why does this happen?
What is going on in the atom with Coulombic attraction?

3. Some Electronegativity Values for Group A Elements
Electronegativity decreases `
Electronegativity increases
High values `
Low values

4. Nonpolar Covalent Bonds
A nonpolar covalent bond
occurs between nonmetals
is an equal or almost equal sharing of electrons
has almost no electronegativity difference (below 0.4)
Examples:
Electronegativity
Atoms Difference Type of Bond
N-N = Nonpolar covalent
Cl-Br = Nonpolar covalent
H-Si = Nonpolar covalent

5. Nonpolar Covalent Bond

6. Polar Covalent Bonds A polar covalent bond
occurs between nonmetal atoms
is an unequal sharing of electrons
has a moderate electronegativity difference (0.4 to 1.7)
Examples:
Electronegativity
Atoms Difference Type of Bond
O-Cl = 0.5 Polar covalent
Cl-C = 0.5 Polar covalent
O-S = 1.0 Polar covalent

7. Polar Covalent Bond

8. Comparing Nonpolar and Polar Covalent Bonds
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings

9. Ionic Bonds An ionic bond occurs between metal and nonmetal ions
is a result of electron transfer
has a large electronegativity difference (above 1.7)
Examples:
Electronegativity
Atoms Difference Type of Bond
Cl-K – 0.8 = Ionic
N-Na 3.0 – = Ionic
S-Cs 2.5 – 0.7 = Ionic

10. Ionic Bond

11. Learning Check
Use the electronegativity difference to identify the type of bond between the following:
nonpolar covalent (NP), polar covalent (P), or
ionic (I).
A. K-N
B. N-O
C. Cl-Cl
D. H-Cl
< 0.4
Nonpolar covalent
0.4 to 1.7
Polar covalent
> 1.7
Ionic
Electronegativity Difference

12. Some Electronegativity Values for Group A Elements
Electronegativity decreases `
Electronegativity increases
High values `
Low values

13. Not all molecules with polar bonds are polar
You will learn more about this when you study molecular geometry

14. Crosscutting Concepts
Patterns
in chemistry, and other sciences, we are always looking for patterns
you were able to determine a pattern of nature of bonds formed when different atoms interact

15. Crosscutting Concepts
Models
in chemistry, and other sciences, we often use models to help us understand phenomenon
you used a computer simulation to model the effect of changing electronegativity

16. Crosscutting Concepts
Structure and Function
in chemistry, and other sciences, the way an object is shaped or structured determines many of its properties and functions
the structure of a molecule determines if it is polar or nonpolar

17. Nature of Science and Scientific Inquiry
Laws vs Theories
law-behavior of natural phenomenon or generalized relationships under certain conditions
theory-well substantiated explanation of some aspect of natural world
theories do not become laws even with additional evidence

18. Nature of Science and Scientific Inquiry
Data vs Evidence
data-measurements, observations, and findings collected as part of an investigation
evidence-analyzed data and interpretation of the analysis