Solutions: Chapter 7

33. a. K; Li; K
b. C; F; C
c. Ca; Mg; Ca
d. S; O; S
34. a. B d. B
b. C
c. D
e. B
D. Essay
35. Ionization energy and electronegativity are
properties that reflect an atom’s ability to
attract and retain electrons. A high ionization
energy indicates that an atom has a tight hold
on its electrons. A high electronegativity
indicates an ability to attract additional
electrons.
Chapter 6 Small-Scale Lab
Analyze and Conclude
1. Fluorine
2. Electronegativity generally increases from
left to right along a period.
3. Metals, which are on the left side of the
table, have lower electronegativity values
than nonmetals, which are on the right.
4. Electronegativity generally increases from
bottom to top within a group. Except for
boron, the rest of Group 3A shows a reverse
in this trend.
5. Although hydrogen is placed in Group 1A
based on its electron configuration, hydrogen
is classified as a nonmetal.
You’re The Chemist
1. Students divide the values of first ionization
energies by 300 and measure the appropriate
length of straws.
2. Students must determine their own scale
before they begin. Students often use two
wells to represent both ionic and atomic
radii. Other students cut a straw to a length
that represents the larger radius of an atom
and mark the straw to show the smaller
radius of the corresponding cation.
3. The value for xenon is similar to iodine,
which is consistent with the general trend.
Based on this value, xenon appears to have
the ability to attract electrons and form
compounds.
780 Core Teaching Resources
Section Review 7.1
Part A Completion
1. valence electrons
2. group
3. electron dot structures
4. octet rule
5. cations
6. anions
7. 1
8. Halide ions
9. gain
10. charges
Part B True/False
11. NT 13. ST 15. AT
12. AT 14. NT 16. NT
Part C Matching
17. b 20. g 22. a
18. d
19. e
21. f 23. c
Part D Questions and Problems
24. a. Si
c.
b.
Rb=
=Ba=
25 a. 2 electrons lost; magnesium ion; cation
b. 2 electrons lost; calcium ion; cation
c. 1 electron gained; bromide ion, anion
d. 1 electron lost; silver ion; cation
26. Nonmetals attain stable noble gas
configurations by gaining electrons and
forming anions with 8 outer electrons in the
existing energy level. Metals attain noble gas
configurations by losing electrons and
forming cations with a complete octet in the
next-lowest energy level.
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.

© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
Section 7.2
Part A Completion
1. electrostatic forces
2. oppositely
3. ionic bonds
4. neutral
5. formula unit
6. crystals
7. high
8. large
9. stable
10. molten
Part B True-False
11. AT 13. AT 15. NT
12. ST 14. ST
Part C Matching
16. b 18. c 20. a
17. e 19. d
Part D Questions and Problems
21. Ionic bonds are the electrostatic forces of
attraction that bind oppositely charged ions
together. In an ionic compound, the positive
charges of the cations equal the negative
charges of the ions.
22. When ionic compounds are melted, the
orderly crystal structure breaks down. Each
ion is then free to move throughout the
molten mass. If a voltage is applied, cations
will migrate to one electrode, and anions will
migrate to the other. This movement of ions
means that there is a flow of electricity
between the two electrodes. When ionic
compounds dissolve in water, their ions are
free to move. Thus, aqueous solutions of ionic
compounds also conduct electricity.
Section 7.3
Part A Completion
1. cations
2. electrons
3. metallic
4. electrical
5. malleable/ductile
6. ductile/malleable
7. body-centered/face-centered
8. face-centered/body-centered
9. hexagonal close-packed
10. alloy
Part B True-False
11. NT 13. NT 15. AT
12. ST 14. AT
Part C Matching
16. d 18. b 20. a
17. e 19. c
Part D Questions and Problems
21. Solid metals consist of closely packed cations
surrounded by free-moving valence
electrons, which make metals good
conductors of electric current. As electrons
enter one end of a bar of metal, an equal
number leave the other end. Metal cations
are insulated from one another by electrons.
When a metal is subjected to pressure, the
metal cations easily slide past one another.
This behavior makes the metal malleable and
ductile.
22. The superior properties of alloys result from
the cumulative properties of all the
constituents of the alloy. For example, an
alloy can be more durable than one
constituent but more malleable than another.
Practice Problems 7
Section 7.1
1. a. (i) 2 (ii) Ba 6 (iii) Ba 2
b. (i) 7 (ii) (iii) I c. (i) 1 (ii) K = (iii) K I
2. a. 3
b. 7
c. 6
3. a. 1s22s22p63s23p64s2 b. 1s 2 2s 2 2p 6 3s 2 3p 5
c. 1s 2 2s 2 2p 6
d. 1s 2 2s 2 2p 6 3s 2 3p 6
e. 1s 2 2s 2 2p 6
4. The number of valence electrons in an atom
of a representative element is the same as the
group number of the element.
Answer Key 781

5. a. loses 2 electrons; cation
b. loses 3 electrons; cation
c. gains 2 electrons; anion
d. loses 1 electron; cation
e. gains 1 electron; anion
f. gains 3 electrons; anion
6. a. chloride ion, Cl b. potassium ion, K
c. oxide ion, O 2
d. barium ion, Ba 2
7. a. 2 lost
b. 1 gained
c. 1 lost
d. 3 lost
8. a. cation d. anion
b. cation e. cation
c. anion f. cation
Section 7.2
1. a. NaBr d. Al 2 O 3
b. Na 2 S e. BaCl 2
c. CaI2 2. Ionic compounds are formed when metals
react with nonmetals. The combinations in b
and c will form ionic compounds
3. The coordination number is the number of
ions of the opposite charge that surround an
ion in a crystal.
4. The coordination number is determined by
using x-ray diffraction crystallography.
Patterns are used to calculate the positions of
ions in the crystal and to define the structure
of the crystal.
Section 7.3
1. A metallic bond is made up of cations that are
surrounded by mobile valence electrons.
2. The metallic crystal is thought to consist of an
array of metal cations in a “sea” of electrons.
Although the electrons are attracted to the
metal cations, no individual electron is
confined to any specific cation; rather, the
electrons are free to move about the
crystalline structure. When electrical current
is applied to a metal, these mobile electrons
can carry charge from one end of the metal to
the other.
3. Metals are crystalline. The metal cations are
arranged in a very compact and orderly
structure or pattern.
782 Core Teaching Resources
4. • Body-centered cubic: every atom (except
those at the surface) has 8 neighbors.
• Face-centered cubic: every atom has
12 neighbors.
• Hexagonal close-packed: every atom has 12
neighbors, but in a different arrangement
than face-centered cubic.
5. An alloy is a mixture of two or more elements,
at least one of which is a metal. Alloys have
properties of metals.
6. a. Brass: copper and zinc
b. Bronze: copper and tin
c. Stainless steel: iron, chromium, carbon,
and nickel
d. Sterling silver: silver and copper
e. Cast iron: iron and carbon
f. Spring steel: iron, chromium, and carbon
Interpreting Graphics 7
1. sodium 1s22s22p63s1 Sodium has 1 valence electron.
chlorine 1s22s22p63s23p5 Chlorine has 7 valence electrons.
2. In Step 1, each sodium atom gives up one
valence electron to a chlorine atom. In this
process, sodium becomes positively charged
and chlorine becomes negatively charged.
Each ion attains the electron configuration of
the nearest noble gas.
3. In Step 2, ionic bonds form between sodium
cations and chlorine anions. The ions arrange
themselves in an orderly, three-dimensional
array characteristic of a crystalline solid. In
NaCl, each ion is surrounded by six other ions
of opposite charge, which results in a very
stable ionic compound.
4. NaCl is typical of many ionic compounds.
The large amount of energy released when an
ionic lattice is formed (Step 2) compensates
for the endothermic nature of the electron
transfer (Step 1). To reverse the lattice
formation through melting would require
enough energy to overcome the multiple
atttractions within the crystal lattice.
Vocabulary Review 7
1. j 6. l 11. b
2. i 7. a 12. k
3. f 8. c 13. m
4. g 9. e
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.