Free Study Guide for
Cracolice • Peters
Introductory Chemistry: An Active Learning Approach
Second Edition
www.brookscole.com/chemistry
Chapter 11
Chemical Bonding
Chapter 11–Assignment A: Ionic and Covalent Bonding
A chemical bond may be defined as a force that holds atoms together to form molecules or
ions (in this assignment) or metals (in Assignment B). The term chemical bond also refers
to the force that holds oppositely charged ions together to form ionic compounds. In all
cases, chemical bonds are formed in a system if the total energy of that system decreases
after the bond is formed. There is a natural tendency towards minimization of energy.
Ionic bonds between atoms appear to form when atoms of a metal lose one, two, or three
electrons to form a cation that is isoelectronic with a noble gas and atoms of a nonmetal gain
one, two, or three electrons to form an anion that is also isoelectronic with a noble gas.
Bonds also form between two nonmetals, both of which have atoms that are one, two, or
even three electrons short of a noble gas electron configuration. This is accomplished
through covalent bonding, in which electrons are shared. Look for these big ideas:
1)
Many monatomic ions are isoelectronic with noble gas atoms, which have an octet
(8) of valence electrons. The “complete octet” is a convenient memory aid.
2)
An ionic bond, also called an electron-transfer bond, is formed because of the
electrostatic attraction between oppositely charged ions.
3)
Covalent bonds form when two atoms achieve a noble gas octet by sharing one or
more pairs of electrons.
Learning Procedures
Study
Sections 11.1–11.3. Focus on Goals 1–6 as you study.
Strategy
As you study ionic and covalent bonds, compare and contrast these bonding
types. We suggest that you set up a table, listing ionic bonding in one
column and covalent bonding in another. Items for comparison should
include: the periodic table and its relationship to ionic vs. covalent bonds,
how atoms achieve noble gas configurations in each bonding type, and
how the phrases electron transfer and electron sharing correlate with the
bonding types.
Answer
Questions, Exercises, and Problems 1–9. Check your answers with those
at the end of the chapter.
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Chapter 11
Workbook
Chemical Bonding
If your instructor recommends the Active Learning Workbook, do
Questions, Exercises, and Problems 1–9.
Chapter 11–Assignment B: More About Covalent Bonding; Metallic Bonds
In Assignment A you learned that covalent bonds are characterized by sharing of electrons.
Are the bonding electrons shared equally? If the bonding electrons are not shared equally,
can we predict which of the two atoms gets the bigger share?
We also see in this assignment that covalent bonding applies to many-atom molecules, and
that the bonds between atoms can involve more than one pair of electrons.
Finally, you will learn about bonding among metal atoms. These are appropriately called
metallic bonds and can be thought of as positively charged metal cations floating in a sea of
negatively charged electrons.
Watch for these key ideas:
1)
In a nonpolar covalent bond, the bonding electrons are shared equally by the bonded
atoms. In a polar covalent bond, one atom attracts the shared electrons more
strongly than the other.
2)
The relative ability of atoms of an element to attract electron pairs in covalent bonds
is expressed by the electronegativity of the element.
3)
The polarity of a bond is estimated by the difference in electronegativities of the
bonded atoms. The atom with the higher electronegativity is the negative end of the
bond. The atom with the lower electronegativity is the positive end of the bond.
4)
Metallic bonding occurs because of attractive forces between negatively charged
valence electrons moving among positively charged metal ions.
Learning Procedures
Study
Sections 11.4–11.8. Focus on Goals 7–12 as you study.
Strategy
This is conceptual material. Study the text carefully, focusing on the
vocabulary and its applications.
Answer
Questions, Exercises, and Problems 10–20. Check your answers with those
at the end of the chapter.
Workbook
If your instructor recommends the Active Learning Workbook, do
Questions, Exercises, and Problems 10–20.
69
Copyright © 2004 Brooks/Cole, a division of Thomson Learning, Inc.
No part of this work may be reproduced without the written permission of the publisher.
Study Guide for Introductory Chemistry: An Active Learning Approach
Chapter 11–Assignment C: Summary and Review
Three models describe the chemical “glue” that holds compounds together. In this
introductory course, we present these models as absolutes: a bond is either ionic (electrondonating) or covalent (electron-sharing) or metallic (electron-sea). In more advanced
courses, you will see that these three models are extremes, used to help you learn how atoms
bond. As in most cases involving extreme positions, the truth is found somewhere in the
middle.
Learn well the trends in electronegativity. It increases from left to right across a period and
also increases from bottom to top in a group. If you remember that F is the most
electronegative element, you can easily remember those trends. Electronegativity is the key
to determining electrostatic attractions in bonds and compounds. In your later chemistry
courses, you will see that electronegativity is the link between many different concepts, and
it makes them all fit together. Don't underestimate its value.
In this chapter and also in Chapter 12 you use the idea of a noble gas electron configuration,
or complete octet. There is no magic in a complete octet; Section 11.8, Exceptions to the
Octet Rule, is proof that the octet rule is fallible. An ionic bond forms because of
electrostatic attractions of the ions, not because of the noble gas electron configurations
those ions happen to have. Use the octet rule for what it is, a memory aid, and no more.
Learning Procedures
Review
your lecture and textbook notes.
the Chapter in Review and the Key Terms and Concepts, and read the Study
Hints and Pitfalls to Avoid.
Answer
Concept-Linking Exercises 1–6. Check your answers with those at the end
of the chapter.
Questions, Exercises, and Problems 21–27. Include Questions 28–32 if
assigned by your instructor. Check your answers with those at the end of the
chapter.
Workbook
If your instructor recommends the Active Learning Workbook, do
Questions, Exercises, and Problems 21–24. Include Questions 25–29 if
assigned by your instructor.
Take
the chapter summary test that follows. Check your answers with those at the
end of this assignment.
Chapter 11 Sample Test
Instructions: You may use a “clean” periodic table.
1)
Which of the following is not an anion?
a) F—
b) NO3 –
c) HPO4 2 –
2)
Which of the following is not isoelectronic with a noble gas?
a) Na+
b) Cl–
c) S2 –
d) Al3+
e) Zn2+
d) K+
e) N3 –
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Chapter 11
Chemical Bonding
3)
A bond formed by the transfer of an electron from one atom to another is called a(n)
_____ bond.
a) ionic
b) covalent
c) metallic
d) nonpolar e) Lewis
4)
Identify the incorrect statement among the following.
a) The bond between hydrogen atoms in H—H is a covalent bond.
b) When two bonding electrons are shared by two atoms, they count as valence
electrons for only the least electronegative atom.
c) The Cl2 bond is formed by the overlap of half-filled 3p orbitals of two chlorine
atoms.
d) The stability of a noble-gas electron configuration contributes to the formation
of a covalent bond.
e) When a covalent bond forms, the charge density is concentrated in the region
between the two nuclei.
5)
How many bonding electron pairs (_____) and how many lone pairs (_____) are in
a nitrogen molecule? : N ≡ N :
6)
Identify each of the following bonds as either primarily ionic or primarily covalent:
a) Na—F
b) Ba—Br
c) C—H
d) N—O
7)
Identify the incorrect statement among the following:
a) The bond between two atoms of the same element is probably less polar than the
bond between two atoms of different elements.
b) The distribution of electronic charge in a polar bond is not symmetrical.
c) A bonding electron pair does not tend to be closer to either of the bonded atoms
if the bond is polar.
d) One end of a polar bond is said to be the negative pole.
e) You can estimate the polarity of a bond by calculating the difference between the
electronegativity values for the bonded elements.
8)
Which of the following best describes the C—O bond?
a) Nonpolar
b) Polar covalent with C as the + end of the bond
c) Polar covalent with O as the + end of the bond
d) Ionic
e) Metallic
9)
Rank the following bonds in order of decreasing polarity:
C—C
C—H
C—N
C—O
10)
Identify the incorrect statement among the following.
a) An alloy is a solid mixture of two or more elements that has macroscopic
metallic properties.
b) The fact that metals are good electrical conductors can be explained theoretically
by the nature of the metallic bond.
c) The electrons in a metallic bond are localized.
d) A metal effectively consists of metal ions surrounded by an electron sea.
e) Metals are found to the left of the stair-step line in the periodic table.
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Study Guide for Introductory Chemistry: An Active Learning Approach
Answers to Chapter 11 Sample Test
1) d 2) e 3) a 4) b 5) 3 bonding electron pairs and 2 lone pairs
6) a and b are primarily ionic; c and d are primarily covalent
7) c 8) b 9) C—O > C—N > C—H > C—C
10) c
72
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No part of this work may be reproduced without the written permission of the publisher.