Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
79
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 8
Practice Problems
12. Use the VSEPR model and the concept of hybridization to
describe the hybrid orbitals and the shape of each of the following molecules.
a. H 2 S
d. NF 3
b. BeF 2
e. BI 3
c. CBr 4
8.5 Electronegativity and Polarity
Electronegativity is a measure of the tendency of an atom to attract
electrons in a chemical bond. The most highly electronegative elements occur in the upper right in the periodic table (disregarding the
noble gases, which rarely form compounds). The least electronegative elements occur in the lower left of the table.
The electronegativity difference between two bonded atoms can
be used to predict the character of the bond. A bond is nonpolar covalent when there is virtually no electronegativity difference. A bond is
polar covalent when there is some electronegativity difference
(unequal electron sharing). A bond is ionic if the electronegativity
difference is very large. An electronegativity difference of more than
1.7 generally means that a bond is more ionic than covalent.
A molecule also may be polar or nonpolar, depending on
whether it contains polar bonds and depending on its shape. For
example, a water molecule is polar because there is a significant
electronegativity difference between the H and O atoms and because
the molecule is bent, not symmetric. There is a negative end near the
more electronegative O atom, and a positive end near the H atoms.
Carbon tetrachloride (CCl 4 ) has polar bonds, but the tetrahedral molecule as a whole is nonpolar because it is symmetric.
The properties of covalent substances vary, depending on a number of factors, including the intermolecular forces. Polar molecules
tend to be soluble in polar solvents, whereas nonpolar molecules
tend to be soluble in nonpolar solvents. For nonpolar molecules, the
intermolecular forces are weak dispersion forces, and melting and
boiling points tend to be low. For polar molecules, there are stronger
dipole-dipole forces whose magnitude depends on the degree of
polarity. If hydrogen is bonded to a highly electronegative atom,
Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
79
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 8
Practice Problems
12. Use the VSEPR model and the concept of hybridization to
describe the hybrid orbitals and the shape of each of the following molecules.
a. H 2 S
d. NF 3
b. BeF 2
e. BI 3
c. CBr 4
8.5 Electronegativity and Polarity
Electronegativity is a measure of the tendency of an atom to attract
electrons in a chemical bond. The most highly electronegative elements occur in the upper right in the periodic table (disregarding the
noble gases, which rarely form compounds). The least electronegative elements occur in the lower left of the table.
The electronegativity difference between two bonded atoms can
be used to predict the character of the bond. A bond is nonpolar covalent when there is virtually no electronegativity difference. A bond is
polar covalent when there is some electronegativity difference
(unequal electron sharing). A bond is ionic if the electronegativity
difference is very large. An electronegativity difference of more than
1.7 generally means that a bond is more ionic than covalent.
A molecule also may be polar or nonpolar, depending on
whether it contains polar bonds and depending on its shape. For
example, a water molecule is polar because there is a significant
electronegativity difference between the H and O atoms and because
the molecule is bent, not symmetric. There is a negative end near the
more electronegative O atom, and a positive end near the H atoms.
Carbon tetrachloride (CCl 4 ) has polar bonds, but the tetrahedral molecule as a whole is nonpolar because it is symmetric.
The properties of covalent substances vary, depending on a number of factors, including the intermolecular forces. Polar molecules
tend to be soluble in polar solvents, whereas nonpolar molecules
tend to be soluble in nonpolar solvents. For nonpolar molecules, the
intermolecular forces are weak dispersion forces, and melting and
boiling points tend to be low. For polar molecules, there are stronger
dipole-dipole forces whose magnitude depends on the degree of
polarity. If hydrogen is bonded to a highly electronegative atom,