1. Chapter 10 Molecular Structure: Liquids and Solids
10.4
Electronegativity and Polarity
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings

2. Electronegativity Electronegativity values
Indicate the attraction of an atom for shared electrons.
Increases from left to right going across a period on the periodic table.
Is high for the nonmetals with fluorine as the highest.
Is low for the metals.

3. Some Electronegativity Values for Group A Elements
Electronegativity increases
High values
Low values
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings

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 (0.0 to 0.4).
Examples:
Atoms Electronegativity Type of Bond Difference
N-N = Nonpolar covalent
Cl-Br = Nonpolar covalent
H-Si = Nonpolar covalent

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

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

7. 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
Cl-K – 0.8 = 2.2 Ionic
N-Na 3.0 – = 2.1 Ionic
S-Cs 2.5 – 0.7 = 1.8 Ionic

8. Predicting Bond Types Table 10.4
Copyright © by Pearson Education, Inc. Publishing as Benjamin Cummings

9. Range of Bond Types Table 10.5
Copyright © by Pearson Education, Inc. Publishing as Benjamin Cummings

10. Learning Check
Use the electronegativity difference to identify the type of bond between the following as:
nonpolar covalent (NP), polar covalent (P), or
ionic (I).
A. K-N
B. N-O
C. Cl-Cl
D. H-Cl

11. Solution nonpolar covalent (NP), polar covalent (P), or ionic (I).
Use the electronegativity difference to identify the type of bond between the following as:
nonpolar covalent (NP), polar covalent (P), or
ionic (I).
A. K-N 2.2 ionic (I)
B. N-O polar covalent (P)
C. Cl-Cl 0.0 nonpolar covalent (NP)
D. H-Cl 0.9 polar covalent (P)

12. Polar Molecules A polar molecule Contains polar bonds.
Has a separation of positive and negative charge called a dipole indicated with + and -.
Has dipoles that do not cancel.
+  • •
H–Cl H—N—H
dipole │ H
dipoles do not cancel

13. Nonpolar Molecules A nonpolar molecule Contains nonpolar bonds.
Cl–Cl H–H
Or has a symmetrical arrangement of polar bonds.
O=C=O Cl │
Cl–C–Cl Cl
dipoles cancel

14. Determining Molecular Polarity
STEP Write the electron-dot formula.
STEP Determine the polarity of the bonds.
STEP Determine if any dipoles cancel or not.
Example: H2O
. .
H─O: H2O is polar │ H
dipoles do not cancel

15. Learning Check Identify each of the following molecules as
1) polar or 2) nonpolar. Explain.
A. PBr3
B. HBr
C. Br2
D. SiBr4

16. Solution Identify each of the following molecules as
1) polar or 2) nonpolar. Explain.
A. PBr ) pyramidal; dipoles don’t cancel; polar
B. HBr 1) linear; one polar bond (dipole); polar
C. Br ) linear; nonpolar bond; nonpolar
D. SiBr ) tetrahedral; dipoles cancel; nonpolar