CHAPTER
Models of the Atom
4
Section 4.1 Dalton Model of the Atom
2.
(c)
“Atoms are indivisible” proved to be invalid with Thomson’s discovery
of the electron and proton.
4.
Dalton relied on the work of (1) Robert Boyle, who first proposed the particle
nature of gases; (2) Antoine Lavoisier, who established the law of conservation of
mass; and (3) Joseph Proust, who established the law of definite composition.
Section 4.2 Thomson Model of the Atom
6.
The pudding represents a homogeneous atom with a positive charge.
8.
The proton (p+) is the simplest positive particle.
10.
The relative charge on a proton (p+) is plus one (+1).
Section 4.3 Rutherford Model of the Atom
12.
Protons and neutrons are found in the atomic nucleus.
14.
The approximate size of an atom is 1 × 10– 8 cm.
16.
The relative mass of an electron to a proton is 1/1836 and 1, respectively.
Section 4.4 Atomic Notation
18.
Isotope
Neutrons
(a)
23
1 1 Na
23 – 11 = 12 n0
(c)
65
3 0 Zn
65 – 30 = 35 n0
Isotope
Neutrons
(b)
27
1 3 Al
27 – 13 = 14 n0
(d)
107
47 Ag
107 – 47 = 60 n0
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Models of the Atom 21
20.
Isotope
Neutrons
Isotope
Neutrons
(a)
hydrogen-2
2 – 1 = 1 n0
(b)
carbon-14
14 – 6 = 8 n0
(c)
cobalt-60
60 – 27 = 33 n0
(d) iodine-131
131 – 53 = 78 n0
22.
24.
Atomic
Notation
Atomic
Number
Mass
Number
Number of
Protons
Number of
Neutrons
Number of
Electrons
19
9
F
9
19
9
10
9
31
15
P
15
31
15
16
15
59
28
Ni
28
59
28
31
28
210
82
Pb
82
210
82
128
82
(a)
16 n0
15 p+
(c)
22 n0
18 p+
15 e–
e–
(b)
18 n0
17 p+
17 e–
18 e–
(d)
78 n0
53 p+
53 e–
Section 4.5 Atomic Mass
26.
The atomic mass is the weighted average of the individual isotopic masses that
occur naturally for an element.
28.
Carbon-12 is the current reference isotope for the atomic mass scale.
30.
2 7Al
32.
31P
34.
Mg-24:
Mg-25:
Mg-26:
22
has only one naturally occurring isotope with a mass of 26.98 amu.
has only one naturally occurring isotope with a mass of 30.97 amu.
Chapter 4
23.985 amu × 0.7870
24.986 amu × 0.1013
25.983 amu × 0.1117
Atomic Mass
=
=
=
=
18.88
2.531
2.902
24.31
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amu
amu
amu
amu
36.
Zn-64:
Zn-66:
Zn-67:
Zn-68:
Zn-70:
63.929 amu × 0.4889
65.926 amu × 0.2781
66.927 amu × 0.0411
67.925 amu × 0.1857
69.925 amu × 0.0062
Atomic Mass
=
=
=
=
=
=
31.25
18.33
2.75
12.61
0.43
65.37
amu
amu
amu
amu
amu
amu
Section 4.6 The Wave Nature of Light
38.
Violet light has a shorter wavelength than blue light.
40.
Violet light has a higher frequency than blue light.
42.
Violet light has higher energy than blue light.
44.
A wavelength of 550 nm has a higher frequency than 650 nm.
Section 4.7 The Quantum Concept
46.
48.
50.
An electron represents the quantum or particle nature of electrical energy.
(a)
(b)
Example
spiral staircase
elevated ramp
Characteristic
quantized
continuous
(a)
(b)
Example
10-mL volumetric pipet
10-mL graduated cylinder
Characteristic
quantized
continuous
Section 4.8 Bohr Model of the Atom
52.
The emission line spectrum of hydrogen was the experimental evidence that
supported the concept of electron energy levels in an atom.
54.
The 2 to 1 transition is the least energetic change because the electron drops from
level 2, which is lower in energy than level 3, or level 4.
56.
Energy Level Change
5 to 2
Spectral Line Color
violet line
58.
Energy Level Change
5 to 4
Type of Emission
infrared energy
60.
The violet line in the emission spectrum has the shortest wavelength.
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Models of the Atom 23
62.
64.
(a)
(b)
Energy Level Change
3 to 2
4 to 2
Number of Photons
100
100
(a)
(b)
(c)
Energy Level Change
5 to 1
5 to 2
5 to 4
Spectral Line Color
ultraviolet line
violet line
infrared line
Section 4.9 Energy Levels and Sublevels
66.
68.
70.
72.
Fine lines in the emission spectra of the elements suggest sublevels within
main energy levels.
(a)
(b)
(c)
(d)
Energy Level
1st level
2nd level
3rd level
4th level
Sublevels
1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
(a)
(b)
(c)
(d)
Sublevel
an s sublevel
a p sublevel
a d sublevel
an f sublevel
Max. Electrons
2 e–
6 e–
10 e–
14 e–
The maximum number of electrons in the fourth energy level is equal to the sum
of the maximum number of electrons in the 4s, 4p, 4d, and 4f sublevels, that is,
2 e– + 6 e– + 10 e– + 14 e– = 32 e– .
Section 4.10 Electron Configuration
74.
The 4d sublevel follows the 5s sublevel.
5s
5p
4s
4p 4d
3s
3p
2s
2p
3d
1s
24
Chapter 4
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76.
78.
(a)
(b)
(c)
(d)
Element
B
Ar
Mn
Ni
Electron Configuration
1s2 2s2 2p1
1s2 2s2 2p6 3s2 3p6
1s2 2s2 2p6 3s2 3p6 4s2 3d5
1s2 2s2 2p6 3s2 3p6 4s2 3d8
(a)
(b)
(c)
(d)
Electron Configuration
1s2 2s2 2p5
1s2 2s2 2p6 3s2 3p6
1s2 2s2 2p6 3s2 3p6 4s2 3d1 0 4p6 5s2 4d5
1s2 2s2 2p6 3s2 3p6 4s2 3d1 0 4p6 5s2 4d1 0 5p5
Element
F
Ar
Tc
I
Section 4.11 Quantum Mechanical Model of the Atom
80.
(a)
(b)
z
↑
z
↑
y
(a)
(c)
84.
Orbitals
Larger Orbital
2s or 3s
2px or 2py
3s
same size
Orbitals
(b) 2px or 3px
(d) 4py or 4pz
Description
(a)
(b)
86.
x
↑
↑
82.
y
Larger Orbital
3px
same size
Orbital
spherical orbital in the 6th energy level
dumbbell-shaped orbital in the 3rd energy level
Sublevel
(a) 1s
(b) 2p
(c) 3d
(d) 4f
x
6s
3p
Max. # of Electrons
2 e–
6 e–
10 e–
14 e–
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Models of the Atom 25
General Exercises
88.
Let X = the mass of Ga-71 isotope
Abundance of Ga-71: 100% – 60.10%
Ga-71 isotope:
Ga-69 isotope:
Both isotopes:
=
39.90%
X × 0.3990
68.92 amu × 0.6010
atomic mass
=
=
=
0.3990 X
41.42 amu
69.72 amu
0.3990 X + 41.42 amu
0.3990 X
0.3990 X
=
=
=
X
=
69.72 amu
69.72 amu – 41.42 amu
28.30 amu
28.30 amu
0.3990
mass of Ga-71 isotope
=
70.93 amu
90.
The periodic table lists a mass number for Pm (147), and not an atomic mass.
We therefore conclude that there is no stable isotope for promethium.
92.
Wavelength
(a) 320 nm
(b) 1500 nm
Region (see Figure 4.9)
ultraviolet
infrared
Challenge Exercises
94.
If the average mass of silver is approximately 108 amu and one isotope is
Ag-109, given an equal abundance, the other isotope must be Ag-107.
96.
An atom is more stable with a completely filled d sublevel than a partially filled
sublevel. If one of the silver 5s electrons drops into the 4d sublevel, the 4d
sublevel is completely filled, and thus the atom is more stable.
Online Exercises
98.
Gold gives rise to the expression “acid test” as the qualitative test for gold is its
inability to react even with strong acids, unlike other metals.
100.
The color of oxygen in the liquid state is pale blue (see Wikipedia).
26
Chapter 4
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