1. Chapter 10 Structures of Solids and Liquids
10.3
Electronegativity and Polarity

2. Electronegativity Electronegativity
is the relative ability of atoms to attract shared electrons
is higher for nonmetals, with fluorine as the highest with a value of 4.0
is lower for metals, with cesium and francium as the lowest with a value of 0.7
increases from left to right going across a period on the periodic table
decreases going down a group on the periodic table

3. Some Electronegativity Values for Group A Elements

4. Learning Check
Using the periodic table, predict the order of increasing electronegativity for the elements O, K, and C.

5. Solution
The metal K on the left of Period 4 has the lowest electronegativity of the three elements. The nonmetal O on the upper right of Period 2 has the highest electronegativity. The nonmetal C, which is on the left of O in the periodic table, has a lower electronegativity than O, but a higher electronegativity than K. Order of increasing electronegativity: K, C, O

6. Nonpolar Covalent Bonds
A nonpolar covalent bond
occurs between nonmetal atoms
consists of an equal (or almost equal) sharing of electrons
has a zero (or close to zero) electronegativity difference of 0.0 to 0.4
Examples:
Atoms Electronegativity Type of Bond Difference
NN = Nonpolar covalent
ClBr = Nonpolar covalent
HSi = Nonpolar covalent

7. Polar Covalent Bonds A polar covalent bond
occurs between nonmetal atoms
consists of atoms that share electrons unequally
has an electronegativity difference range of 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

8. Comparing Nonpolar and Polar Covalent Bonds

9. 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 = Ionic
NNa 3.0 – = Ionic
SCs 2.5 – 0.7 = Ionic

10. Electronegativity and Bond Types

11. Predicting Bond Types

12. Learning Check
Use electronegativity differences to classify each of the following bonds as nonpolar covalent (NP), polar covalent (P), or ionic (I):
A bond between
A. K and N
B. N and O
C. Cl and Cl
D. H and Cl

13. Solution Atoms in Electronegativity Type of Bond Difference Bond
A. K and N ionic (I)
B. N and O polar covalent (P)
C. Cl and Cl nonpolar covalent (NP)
D. H and Cl polar covalent (P)

14. Polar Molecules A polar molecule contains polar bonds
has a separation of positive and negative charge called a dipole indicated by a dipole arrow
has dipoles that do not cancel

15. Nonpolar Molecules A nonpolar molecule
may contain identical atoms (nonpolar bonds)
may have a symmetrical arrangement of polar bonds that cancel dipoles

16. Determining Molecular Polarity
The polarity of a molecule is determined from its
electron-dot formula
shape
polarity of the bonds
dipole cancellation

17. Learning Check Identify each of the following molecules as
(P) polar or (NP) nonpolar:
A. PBr3
B. HBr
C. Br2
D. SiBr4

18. Solution Identify each of the following molecules as
(P) polar or (NP) nonpolar:
A. PBr (P) pyramidal; dipoles don’t cancel; polar
B. HBr (P) linear; one polar bond (dipole); polar
C. Br (NP) linear; nonpolar bond; nonpolar
D. SiBr4 (NP) tetrahedral; dipoles cancel; nonpolar