CHAPTER SEVEN
ATOMIC STRUCTURE AND PERIODICITY
For Review
1.
Wavelength: the distance between two consecutive peaks or troughs in a wave
Frequency: the number of waves (cycles) per second that pass a given point in space
Photon energy: the discrete units by which all electromagnetic radiation transmits energy;
EMR can be viewed as a stream of “particles” called photons. Each photon has a unique
quantum of energy associated with it; the photon energy is determined by the frequency (or
wavelength) of the specific EMR.
Speed of travel: all electromagnetic radiation travels at the same speed, c, the speed of light;
c = 2.9979 × 108 m/s
 = c, E = h = hc/: From these equations, wavelength and frequency are inversely related,
photon energy and frequency are directly related, and photon energy and wavelength are
inversely related. Thus, the EMR with the longest wavelength has the lowest frequency and
least energetic photons. The EMR with the shortest wavelength has the highest frequency and
most energetic photons. Using Figure 7.2 to determine the wavelengths, the order is:
wavelength: gamma rays < ultraviolet < visible < microwaves
frequency: microwaves < visible < ultraviolet < gamma rays
photon energy: microwaves < visible < ultraviolet < gamma rays
speed: all travel at the same speed, c, the speed of light
2.
The Bohr model assumes that the electron in hydrogen can orbit the nucleus at specific
distances from the nucleus. Each orbit has a specific energy associated with it. Therefore, the
electron in hydrogen can only have specific energies; not all energies are allowed. The term
quantized refers to the allowed energy levels for the electron in hydrogen.
The great success of the Bohr model is that it could explain the hydrogen emission spectrum.
The electron in H, moves about the allowed energy levels by absorbing or emitting certain
photons of energy. The photon energies absorbed or emitted must be exactly equal to the
energy difference between any two allowed energy levels. Because not all energies are
allowed in hydrogen (energy is quantized), then not all energies of EMR are
absorbed/emitted.
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205
The Bohr model predicted the exact wavelengths of light that would be emitted for a hydrogen atom. Although the Bohr model has great success for hydrogen and other 1 electron ions,
it does not explain emission spectra for elements/ions having more than one electron. The
fundamental flaw is that we cannot know the exact motion of an electron as it moves about
the nucleus; therefore, well defined circular orbits are not appropriate.
3.
Planck’s discovery that heated bodies give off only certain frequencies of light and Einstein’s
study of the photoelectric effect support the quantum theory of light. The wave-particle
duality is summed up by saying all matter exhibits both particulate and wave properties.
Electromagnetic radiation, which was thought to be a pure waveform, transmits energy as if it
has particulate properties. Conversely, electrons, which were thought to be particles, have a
wavelength associated with them. This is true for all matter. Some evidence supporting wave
properties of matter are:
1. Electrons can be diffracted like light.
2. The electron microscope uses electrons in a fashion similar to the way in which light
is used in a light microscope.
However, wave properties of matter are only important for small particles with a tiny mass,
e.g., electrons. The wave properties of larger particles are not significant.
4.
Four scientists whose work was extremely important to the development of the quantum
mechanical model were Niels Bohr, Louis deBroglie, Werner Heisenberg, and Erwin
Schrödinger. The Bohr model of the atom presented the idea of quantized energy levels for
electrons in atoms. DeBroglie came up with the relationship between mass and wavelength,
supporting the idea that all matter (especially tiny particles like electrons) exhibits wave
properties as well as the classic properties of matter. Heisenberg is best known for his
uncertainty principle which states there is a fundamental limitation to just how precisely we
can know both the position and the momentum of a particle at a given time. If we know one
quantity accurately, we cannot absolutely determine the other. The uncertainty principle,
when applied to electrons, forbids well-defined circular orbits for the electron in hydrogen, as
presented in the Bohr model. When we talk about the location of an electron, we can only talk
about the probability of where the electron is located. Schrödinger put the ideas presented by
the scientists of the day into a mathematical equation. He assumed wave motion for the
electron. The solutions to this complicated mathematical equation give allowed energy levels
for the electrons. These solutions are called wave functions, , and the allowed energy levels
are often referred to as orbitals. In addition, the square of the wave function (2) indicates the
probability of finding an electron near a particular point in space. When we talk about the
shape of an orbital, we are talking about a surface that encompasses where the electron is
located 90% of the time. The key is we can only talk about probabilities when referencing
electron location.
5.
Quantum numbers give the allowed solutions to Schrödinger equation. Each solution is an
allowed energy level called a wave function or an orbital. Each wave function solution is
described by three quantum numbers, n, , and m. The physical significance of the quantum
numbers are:
n: Gives the energy (it completely specifies the energy only for the H atom or ions with
one electron) and the relative size of the orbitals.
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ℓ: Gives the type (shape) of orbital.
mℓ: Gives information about the direction in which the orbital is pointing.
The specific rules for assigning values to the quantum numbers n, ℓ, and mℓ are covered in
Section 7.6. In Section 7.8, the spin quantum number ms is discussed. Since we cannot locate
electrons, we cannot see if they are spinning. The spin is a convenient model. It refers to the
ability of the two electrons that can occupy any specific orbital to produce two different
oriented magnetic moments.
6.
The 2p orbitals differ from each other in the direction in which they point in space. The 2p
and 3p orbitals differ from each other in their size, energy and number of nodes. A nodal surface in an atomic orbital is a surface in which the probability of finding an electron is zero.
The 1p, 1d, 2d, 1f, 2f, and 3f orbitals are not allowed solutions to the Schrödinger equation.
For n = 1,   1, 2, 3, etc., so 1p, 1d, and 1f orbitals are forbidden. For n = 2,   2, 3, 4, etc.,
so 2d and 2f orbitals are forbidden. For n = 3,   3, 4, 5, etc., so 3f orbitals are forbidden.
The penetrating term refers to the fact that there is a higher probability of finding a 4s
electron closer to the nucleus than a 3d electron. This leads to a lower energy for the 4s
orbital relative to the 3d orbitals in polyelectronic atoms and ions.
7.
The four blocks are the s, p, d, and f blocks. The s block contains the alkali and alkaline earth
metals (Groups 1A and 2A). The p block contains the elements in Groups 3A, 4A, 5A, 6A,
7A, and 8A. The d block contains the transition metals. The f block contains the inner
transition metals. The energy ordering is obtained by sequentially following the atomic
numbers of the elements through the periodic table while keeping track of the various blocks
you are transversing. The periodic table method for determining energy ordering is illustrated
in Figure 7.27.
The Aufbau principle states that as protons are added one by one to the nucleus to build up
the elements, electrons are similarly added to hydrogenlike orbitals. The main assumptions
are that all atoms have the same types of orbitals and that the most stable electron
configuration, the ground state, has the electrons occupying the lowest energy levels first.
Hund’s rule refers to adding electrons to degenerate (same energy) orbitals. The rule states
that the lowest energy configuration for an atom is the one having the maximum number of
unpaired electrons allowed by the Pauli exclusion principle. The Pauli exclusion principle
states that in a given atom, no two electrons can have the same four quantum numbers. This
corresponds to having only two electrons in any one orbital and they must have opposite
“spins”.
The two major exceptions to the predicted electron configurations for elements 1-36 are Cr
and Cu. The expected electron configurations for each are:
Cr: [Ar]4s23d4 and Cu: [Ar]4s23d9
The actual electron configurations are:
Cr: [Ar]4s13d5 and Cu: [Ar]4s13d10
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207
8.
Valence electrons are the electrons in the outermost principle quantum level of an atom
(those electrons in the highest n value orbitals). The electrons in the lower n value orbitals are
all inner core or just core electrons. The key is that the outer most electrons are the valence
electrons. When atoms interact with each other, it will be the outermost electrons that are
involved in these interactions. In addition, how tightly the nucleus holds these outermost
electrons determines atomic size, ionization energy and other properties of atoms. Elements
in the same group have similar valence electron configurations and, as a result, have similar
chemical properties.
9.
Ionization energy: P(g) → P+(g) + e; electron affinity: P(g) + e → P(g)
Across a period, the positive charge from the nucleus increases as protons are added. The
number of electrons also increase, but these outer electrons do not completely shield the
increasing nuclear charge from each other. The general result is that the outer electrons are
more strongly bound as one goes across a period which results in larger ionization energies
(and smaller size).
Aluminum is out of order because the electrons in the filled 3s orbital shield some of the
nuclear charge from the 3p electron. Hence, the 3p electron is less tightly bound than a 3s
electron, resulting in a lower ionization energy for aluminum as compared to magnesium.
The ionization energy of sulfur is lower than phosphorus because of the extra electronelectron repulsions in the doubly occupied sulfur 3p orbital. These added repulsions, which
are not present in phosphorus, make it slightly easier to remove an electron from sulfur as
compared to phosphorus.
As successive electrons are removed, the net positive charge on the resultant ion increases.
This increase in positive charge binds the remaining electrons more firmly, and the ionization
energy increases.
The electron configuration for Si is 1s22s22p63s23p2. There is a large jump in ionization
energy when going from the removal of valence electrons to the removal of core electrons.
For silicon, this occurs when the fifth electron is removed since we go from the valence
electrons in n = 3 to the core electrons in n = 2. There should be another big jump when the
thirteenth electron is removed, i.e., when a 1s electron is removed.
10.
Both trends are a function of how tightly the outermost electrons are held by the positive
charge in the nucleus. An atom where the outermost electrons are held tightly will have a
small radius and a large ionization energy. Conversely, an atom where the outermost
electrons are held weakly will have a large radius and a small ionization energy. The trends of
radius and ionization energy should be opposite of each other.
Electron affinity is the energy change associated with the addition of an electron to a gaseous
atom. Ionization energy is the energy it takes to remove an electron from a gaseous atom.
Because electrons are always attracted to the positive charge of the nucleus, energy will
always have to be added to break the attraction and remove the electron from a neutral
charged atom. Ionization energies are always endothermic for neutral charged atoms. Adding
an electron is more complicated. The added electron will be attracted to the nucleus; this
attraction results in energy being released. However, the added electron will encounter the
other electrons which results in electron-electron repulsions; energy must be added to
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ATOMIC STRUCTURE AND PERIODICITY
overcome these repulsions. Which of the two opposing factors dominates determines whether
the overall electron affinity for an element is exothermic or endothermic.
Questions
15.
The equations relating the terms are  = c, E = h, and E = hc/. From the equations,
wavelength and frequency are inversely related, photon energy and frequency are directly
related, and photon energy and wavelength are inversely related. The unit of 1 Joule (J) = 1
kg m2/s2. This is why you must change mass units to kg when using the deBroglie equation.
16.
The photoelectric effect refers to the phenomenon in which electrons are emitted from the
surface of a metal when light strikes it. The light must have a certain minimum frequency
(energy) in order to remove electrons from the surface of a metal. Light having a frequency
below the minimum results in no electrons being emitted, while light at or higher than the
minimum frequency does cause electrons to be emitted. For light having a frequency higher
than the minimum frequency, the excess energy is transferred into kinetic energy for the
emitted electron. Albert Einstein explained the photoelectric effect by applying quantum
theory.
17.
Sample Exercise 7.3 calculates the deBroglie wavelength of a ball and of an electron. The
ball has a wavelength on the order of 10 34 m. This is incredibly short and, as far as the waveparticle duality is concerned, the wave properties of large objects are insignificant. The
electron, with its tiny mass, also has a short wavelength; on the order of 10 10 m. However,
this wavelength is significant as it is on the same order as the spacing between atoms in a
typical crystal. For very tiny objects like electrons, the wave properties are important. The
wave properties must be considered, along with the particle properties, when hypothesizing
about the electron motion in an atom.
18.
The Bohr model was an important step in the development of the current quantum
mechanical model of the atom. The idea that electrons can only occupy certain, allowed
energy levels is illustrated nicely (and relatively easily). We talk about the Bohr model to
present the idea of quantized energy levels.
19.
For the radial probability distribution, the space around the hydrogen nucleus is cut-up into a
series of thin spherical shells. When the total probability of finding the electron in each
spherical shell is plotted versus the distance from the nucleus, we get the radial probability
distribution graph. The plot initially shows a steady increase with distance from the nucleus,
reaches a maximum, then shows a steady decrease. Even though it is likely to find an electron
near the nucleus, the volume of the spherical shell close to the nucleus is tiny, resulting in a
low radial probability. The maximum radial probability distribution occurs at a distance of
5.29 × 10 2 nm from the nucleus; the electron is most likely to be found in the volume of the
shell centered at this distance from the nucleus. The 5.29 × 10 2 nm distance is the exact
radius of innermost (n = 1) orbit in the Bohr model.
20.
The width of the various blocks in the periodic table is determined by the number of electrons
that can occupy the specific orbital(s). In the s block, we have 1 orbital ( = 0, m = 0) which
can hold two electrons; the s block is 2 elements wide. For the f block, there are 7 degenerate
f orbitals ( = 3, m = 3, 2, 1, 0, 1, 2, 3), so the f block is 14 elements wide. The g block
CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
209
corresponds to  = 4. The number of degenerate g orbitals is 9. This comes from the 9
possible m values when  = 4 (m = 4, 3, 2, 1, 0, 1, 2, 3, 4). With 9 orbitals, each orbital
holding two electrons, the g block would be 18 elements wide. The h block has  = 5, m =
5, 4, 3, 2, 1, 0, 1, 2, 3, 4, 5. With 11 degenerate h orbitals, the h block would be 22
elements wide.
21.
If one more electron is added to a half-filled subshell, electron-electron repulsions will
increase since two electrons must now occupy the same atomic orbital. This may slightly
decrease the stability of the atom. Hence, half-filled subshells minimize electron-electron
repulsions.
22.
Size decreases from left to right and increases going down the periodic table. So, going one
element right and one element down would result in a similar size for the two elements
diagonal to each other. The ionization energies will be similar for the diagonal elements since
the periodic trends also oppose each other. Electron affinities are harder to predict, but atoms
with similar size and ionization energy should also have similar electron affinities.
23.
The valence electrons are strongly attracted to the nucleus for elements with large ionization
energies. One would expect these species to readily accept another electron and have very
exothermic electron affinities. The noble gases are an exception; they have a large IE but
have an endothermic EA. Noble gases have a stable arrangement of electrons. Adding an
electron disrupts this stable arrangement, resulting in unfavorable electron affinities.
24.
Electron-electron repulsions become more important when we try to add electrons to an atom.
From the standpoint of electron-electron repulsions, larger atoms would have more favorable
(more exothermic) electron affinities. Considering only electron-nucleus attractions, smaller
atoms would be expected to have the more favorable (more exothermic) EA's. These trends
are exactly the opposite of each other. Thus, the overall variation in EA is not as great as
ionization energy in which attractions to the nucleus dominate.
25.
For hydrogen and one-electron ions (hydrogenlike ions), all atomic orbitals with the same n
value have the same energy. For polyatomic atoms/ions, the energy of the atomic orbitals also
depends on ℓ. Because there are more nondegenerate energy levels for polyatomic atoms/ions
as compared to hydrogen, there are many more possible electronic transitions resulting in
more complicated line spectra.
26.
Each element has a characteristic spectrum because each element has unique energy levels.
Thus, the presence of the characteristic spectral lines of an element confirms its presence in
any particular sample.
27.
Yes, the maximum number of unpaired electrons in any configuration corresponds to a
minimum in electron-electron repulsions.
28.
The electron is no longer part of that atom. The proton and electron are completely separated.
29.
Ionization energy is for removal of the electron from the atom in the gas phase. The work
function is for the removal of an electron from the solid.
M(g) → M+(g) + e ionization energy; M(s) → M+(s) + e work function
210
30.
CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
Li+ ions are the smallest of the alkali metal cations and will be most strongly attracted to the
water molecules.
Exercises
Light and Matter
c
2.998  10 8 m / s

= 4.5 × 1014 s 1
1m
λ 660 nm 
1  10 9 nm
31.
 = c,  =
32.
99.5 MHz = 99.5 × 106 Hz = 99.5 × 106 s 1 ;  =
33.
ν=
c 2.998  10 8 m / s

= 3.01 m
v
99.5  10 6 s 1
c 3.00  10 8 m / s

= 3.0 × 1010 s 1
2
λ
1.0  10 m
E = hν = 6.63 × 10-34 J s × 3.0 × 1010 s 1 = 2.0 × 10 23 J/photon
2.0  10 23 J
6.01  10 23 photons

= 12 J/mol
photon
mol
34.
E = hν =
hc 6.63  10 34 J s  3.00  10 8 m / s

= 8.0 × 10 18 J/photon
1m
λ
25 nm 
1  10 9 nm
8.0  10 18 J 6.02  10 23 photons

= 4.8 × 106 J/mol
photon
mol
35.
The wavelength is the distance between consecutive wave peaks.
wavelengths and wave b shows 8 wavelengths.
Wave a shows 4
1.6  10 3 m
Wave a: λ =
= 4.0 × 10 4 m
4
Wave b: λ =
1.6  10 3 m
= 2.0 × 10 4 m
8
Wave a has the longer wavelength. Frequency and photon energy are both inversely
proportional to wavelength, thus wave b will have the higher frequency and larger photon
energy because it has the shorter wavelength.
ν=
c 3.00  10 8 m / s

= 1.5 × 1012 s 1
λ
2.0  10  4 m
CHAPTER 7
E=
ATOMIC STRUCTURE AND PERIODICITY
211
hc 6.63  10 34 J s  3.00  10 8 m / s

= 9.9 × 10 22 J
λ
2.0  10  4 m
Both waves are examples of electromagnetic radiation, so both waves travel at the same
speed, c, the speed of light. From Figure 7.2 of the text, both of these waves represent
infrared electromagnetic radiation.
36.
Referencing figure 7.2 of the text, 2.12 × 10 10 m electromagnetic radiation is X-rays.
λ=
c 2.9979  10 8 m / s

= 2.799 m
ν
107 .1  10 6 s 1
From the wavelength calculated above, 107.1 MHz electromagnetic radiation is FM
radiowaves.
hc 6.626  10 34 J s  2.998  10 8 m / s

λ=
= 5.00 × 10 7 m
19
E
3.97  10 J
The 3.97 × 10 19 J/photon electromagnetic radiation is visible (green) light.
The photon energy and frequency order will be the exact opposite of the wavelength ordering
because E and ν are both inversely related to λ. From the calculated wavelengths above, the
order of photon energy and frequency are:
FM radiowaves < visible (green) light < X-rays
longest λ
shortest λ
lowest ν
highest ν
smallest E
largest E
37.
Ephoton =
hc
6.626  10 34 J s  2.998  108 m / s

= 1.32 × 10 18 J
1m
λ
150 . nm 
1 10 9 nm
1.98 × 105 J ×
38.
a.  =
1 photon
1 atom C
= 1.50 × 1023 atoms C

18
photon
1.32  10 J
c 3.00  10 8 m / s

= 5.0 × 10 6 m
ν
6.0  1013 s 1
b. From Figure 7.2, this is infrared EMR.
c. E = h = 6.63 × 10 34 J s × 6.0 × 1013 s 1 = 4.0 × 10 20 J/photon
4.0  10 20 J 6.0221  10 23 photons

= 2.4 × 104 J/mol
photon
mol
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CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
d. Frequency and photon energy are directly related (E = hv). Because 5.4 × 1013 s 1 EMR
has a lower frequency than 6.0 × 1013 s 1 EMR, the 5.4 × 1013 s 1 EMR will have less
energetic photons.
39.
The energy needed to remove a single electron is:
279 .7 kJ
1 mol
= 4.645 × 10 22 kJ = 4.645 × 10 19 J

23
mol
6.0221  10
E=
40.
41.
hc
hc 6.6261  10 34 J s  2.9979  10 8 m / s
, λ

= 4.277 × 10 7 m = 427.7 nm
19
λ
E
4.645  10 J
208 .4 kJ
1 mol
= 3.461 × 10 22 kJ = 3.461 × 10 19 J to remove one electron

23
mol
6.0221  10
E=
hc
hc 6.6261  10 34 J s  2.9979  10 8 m / s
, λ

= 5.739 × 10 7 m = 573.9 nm
λ
E
3.461  10 19 J
a.
10.% of speed of light = 0.10 × 3.00 × 108 m/s = 3.0 × 107 m/s
λ=
h
6.63  10 34 J s
, λ 
= 2.4 × 10 11 m = 2.4 × 10 2 nm
31
7
mv
9.11  10 kg  3.0  10 m / s
Note: For units to come out, the mass must be in kg since 1 J =
b.
λ
1 kg m 2
s2
h
6.63  10 34 J s

= 3.4 × 10 34 m = 3.4 × 10 25 nm
mv 0.055 kg  35 m / s
This number is so small that it is insignificant. We cannot detect a wavelength this small.
The meaning of this number is that we do not have to worry about the wave properties of
large objects.
42.
43.
a.
λ
h
6.626  10 34 J s

= 1.32 × 10 13 m
mv 1.675  10  27 kg  (0.0100  2.998  10 8 m/s)
b.
λ
h
h
6.626  10 34 J s
, v

= 5.3 × 103 m/s
mv
λm 75  10 12 m  1.675  10  27 kg
λ=
6.63  10 34 J s
h
h
27
=
= 1.6 × 10
kg
, m
15
8
mv
λv 1.5  10 m  (0.90  3.00  10 m/s)
This particle is probably a proton or a neutron.
CHAPTER 7
44.
λ=
ATOMIC STRUCTURE AND PERIODICITY
213
h
h
7
; For λ = 1.0 × 102 nm = 1.0 × 10 m:
, v
mv
λm
v =
6.63  10 34 J s
= 7.3 × 103 m/s
31
7
9.11  10 kg  1.0  10 m
For λ = 1.0 nm = 1.0 × 10 9 m: v =
6.63  10 34 J s
= 7.3 × 105 m/s
9.11  10 31 kg  1.0  10 9 m
Hydrogen Atom: The Bohr Model
45.
For the H atom (Z = 1): En = -2.178 × 10-18 J/n 2; For a spectral transition, ΔE = Ef  Ei:
 1
1 
ΔE = -2.178 × 10 18 J  2  2 
 nf ni 
where ni and nf are the levels of the initial and final states, respectively. A positive value of
ΔE always corresponds to an absorption of light, and a negative value of ΔE always
corresponds to an emission of light.
1 
 1
1 1
a. ΔE = 2.178 × 10 18 J  2  2  = 2.178 × 10 18 J   
3 
2
 4 9
ΔE = 2.178 × 10 18 J × (0.2500  0.1111) = 3.025 × 10 19 J
The photon of light must have precisely this energy (3.025 × 10 19 J).
| ΔE | = Ephoton = hν =
6.6261  10 34 J s  2.9979  10 8 m / s
hc
hc
=
or λ =
λ
| ΔE |
3.025  10 19 J
= 6.567 × 10 7 m = 656.7 nm
From Figure 7.2, this is visible electromagnetic radiation (red light).
1 
 1
b. ΔE = -2.178 × 10 18 J  2  2  = -4.084 × 10 19 J
4 
2
λ
6.6261  10 34 J s  2.9979  10 8 m / s
hc
=
= 4.864 × 10 7 m = 486.4 nm
| ΔE |
4.084  10 19 J
This is visible electromagnetic radiation (green-blue light).
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CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
1 
1
c. ΔE = -2.178 × 10 18 J  2  2  = 1.634 × 10 18 J
2 
1
6.6261  10 34 J s  2.9979  10 8 m / s
λ
1.634  10 18 J
= 1.216 × 10 7 m = 121.6 nm
This is ultraviolet electromagnetic radiation.
46.
1 
 1
a. ΔE = 2.178 × 10 18 J  2  2  = 1.059 × 10 19 J
4 
3
6.6261  10 34 J s  2.9979  10 8 m / s
hc
=
= 1.876 × 10 6 m = 1876 nm
1.059  10 19 J
| ΔE |
λ
From Figure 7.2, this is infrared electromagnetic radiation.
1 
 1
b. ΔE = 2.178 × 10 18 J  2  2  = 4.901 × 10 20 J
5 
4
λ
6.6261  10 34 J s  2.9979  10 8 m / s
hc
=
= 4.053 × 10 6 m
| ΔE |
4.901  10  20 J
= 4053 nm (infrared)
1 
 1
c. ΔE = 2.178 × 10 18 J  2  2  = 1.549 × 10 19 J
5 
3
λ
47.
6.6261  10 34 J s  2.9979  10 8 m / s
hc
=
= 1.282 × 10 6 m
| ΔE |
1.549  10 19 J
= 1282 nm (infrared)
5
4
3
a. 3 → 2
a
b
b. 4 → 2
E 2
c. 2 → 1
c
Energy levels are not to scale.
n=1
CHAPTER 7
5
4
3
48.
E 2
ATOMIC STRUCTURE AND PERIODICITY
215
b
a
c
a. 4 → 3
b. 5 → 4
c. 5 → 3
n=1
Energy levels are not to scale.
49.
 1
1 
1
 1
ΔE = 2.178 × 10 18 J  2  2  = 2.178 10 18 J  2  2  = 2.091 × 10 18 J = Ephoton
1 
5
 nf ni 
λ
6.6261  10 34 J s  2.9979  10 8 m / s
hc
=
= 9.500 × 10 8 m = 95.00 nm
2.091  10 18 J
E
Because wavelength and energy are inversely related, visible light (λ ≈ 400  700 nm) is not
energetic enough to excite an electron in hydrogen from n = 1 to n = 5.
1 
 1
ΔE = 2.178 × 10 18 J  2  2  = 4.840 × 10 19 J
2 
6
6.6261  10 34 J s  2.9979  10 8 m / s
hc
=
= 4.104 × 10 7 m = 410.4 nm
λ
18
E
4.840  10 J
Visible light with λ = 410.4 nm will excite an electron from the n = 2 to the n
= 6 energy level.
50.
a. False; It takes less energy to ionize an electron from n = 3 than from the ground state.
b. True
c. False; The energy difference from n = 3 → n = 2 is less than the energy difference from
n = 3 → n = 1, thus, the wavelength is larger for n = 3 → n = 2 than for n = 3 → n = 1.
d. True
e. False; n = 2 is the first excited state and n = 3 is the second excited state.
51.
Ionization from n = 1 corresponds to the transition ni = 1 → nf =  where E = 0.
1
ΔE = E  E1 = E1 = 2.178 × 10 18  2  = 2.178 × 10 18 J = Ephoton
1 
λ
6.6261  10 34 J s  2.9979  10 8 m / s
hc
=
= 9.120 × 10 8 m = 91.20 nm
18
2
.
178

10
J
E
216
CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
 1
To ionize from n = 2, ΔE = E∞  E2 = E2 = 2.178 × 10 18  2  = 5.445 × 10 19 J
2 
λ
52.
6.6261  10 34 J s  2.9979  10 8 m / s
5.445  10 19 J
= 3.648 × 10 7 m = 364.8 nm
 1 
ΔE = E  En = -En = 2.178 × 10 18 J  2 
n 
Ephoton =
6.626  10 34 J s  2.9979  10 8 m / s
hc
=
= 1.36 × 10 19 J
9
1460  10 m
λ
 1 
Ephoton = ΔE = 1.36 × 10 19 J = 2.178 × 10 18  2 , n2 = 16.0, n = 4
n 
53.
| ΔE| = Ephoton = h = 6.662 × 10 34 J s × 6.90 × 1014 s 1 = 4.57 × 10 19 J
ΔE = 4.57 × 10 19 J because we have an emission.
1 
 1
4.57 × 10 19 J = En – E5 = 2.178 × 10 18 J  2  2  ,
5 
n
1
1
1

= 0.210,
= 0.250, n2 = 4, n = 2
2
25
n
n2
The electronic transition is from n = 5 to n = 2.
54.
| ΔE | = Ephoton =
hc 6.6261  10 34 J s  2.9979  10 8 m / s

= 10 19 = 5.001 × 10 19 J
9
λ
397 .2  10 m
ΔE = -5.001 × 10 19 J because we have an emission.
1 
 1
5.001 × 10 19 J = E2  En = 2.178 × 10 18 J  2  2 
n 
2
0.2296 =
1 1
1
 2 , 2 = 0.0204, n = 7
4 n
n
Quantum Mechanics, Quantum Numbers, and Orbitals
55.
a. Δ(mv) = mΔv = 9.11 × 10 31 kg × 0.100 m/s =
9.11  10 32 kg m
s
CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
Δ(mv)  Δx >
217
6.626  10 34 J s
h
h
, Δx =
=
4  3.142  (9.11  10 32 kg m / s)
4πΔ(mv)
4π
= 5.79 × 10 4 m
b.
Δx =
6.626  10 34 J s
h
=
= 3.64 × 10 33 m
4  3.142  0.145 kg  0.100 m / s)
4πΔ(mv)
c. The diameter of an H atom is roughly 1.0 × 10 8 cm. The uncertainty in position is much
larger than the size of the atom.
d. The uncertainty is insignificant compared to the size of a baseball.
56.
Units of ΔE  Δt = J × s, the same as the units of Planck's constant.
Units of Δ(mv)  Δx = kg ×
m
kg m 2 kg m 2
m

s  Js
s
s
s2
57.
n = 1, 2, 3, ... ; ℓ = 0, 1, 2, ... (n - 1); mℓ = -ℓ ... -2, -1, 0, 1, 2, ...+ℓ
58.
1p: n = 1, ℓ = 1 is not possible; 3f: n = 3, ℓ = 3 is not possible; 2d: n = 2, ℓ = 2 is not
possible; In all three incorrect cases, n = ℓ. The maximum value ℓ can have is n - 1, not n.
59.
b. For ℓ = 3, mℓ can range from -3 to +3; thus +4 is not allowed.
c. n cannot equal zero.
60.
d. ℓ cannot be a negative number.
a. For n = 3, ℓ = 3 is not possible.
d. ms cannot equal 1.
e. ℓ cannot be a negative number.
f.
For ℓ = 1, mℓ cannot equal 2.
61.
ψ2 gives the probability of finding the electron at that point.
62.
The diagrams of the orbitals in the text give only 90% probabilities of where the electron may
reside. We can never be 100% certain of the location of the electrons due to Heisenburg’s
uncertainty principle.
218
CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
Polyelectronic Atoms
63.
5p: three orbitals; 3d z 2 : one orbital; 4d: five orbitals
n = 5: ℓ = 0 (1 orbital), ℓ = 1 (3 orbitals), ℓ = 2 (5 orbitals), ℓ = 3 (7 orbitals),
ℓ = 4 (9 orbitals)
Total for n = 5 is 25 orbitals.
n = 4: ℓ = 0 (l), ℓ = 1 (3), ℓ = 2 (5), ℓ = 3 (7); Total for n = 4 is 16 orbitals.
64.
1p, 0 electrons (ℓ≠ 1 when n = 1); 6d x 2  y 2 , 2 electrons (specifies one atomic orbital); 4f, 14
electrons (7 orbitals have 4f designation); 7py, 2 electrons (specifies one atomic orbital); 2s,
2 electrons (specifies one atomic orbital); n = 3, 18 electrons (3s, 3p and 3d orbitals are
possible; there are one 3s orbital, three 3p orbitals and five 3d orbitals).
65.
a. n = 4: ℓ can be 0, 1, 2, or 3. Thus we have s (2 e ), p (6 e ), d (10 e ) and f (14 e )
orbitals present. Total number of electrons to fill these orbitals is 32.
b. n = 5, mℓ = +1: For n = 5, ℓ = 0, 1, 2, 3, 4. For ℓ = 1, 2, 3, 4, all can have mℓ = +1. Four
distinct orbitals, thus 8 electrons.
c. n = 5, ms = +1/2: For n = 5, ℓ = 0, 1, 2, 3, 4. Number of orbitals = 1, 3, 5, 7, 9 for each
value of ℓ, respectively. There are 25 orbitals with n = 5. They can hold 50 electrons and
25 of these electrons can have ms = +1/2.
d. n = 3, ℓ = 2: These quantum numbers define a set of 3d orbitals. There are 5 degenerate
3d orbitals which can hold a total of 10 electrons.
e. n = 2, ℓ = 1: These define a set of 2p orbitals. There are 3 degenerate 2p orbitals which
can hold a total of 6 electrons.
66.
a. It is impossible to have n = 0. Thus, no electrons can have this set of quantum numbers.
b. The four quantum numbers completely specify a single electron in a 2p orbital.
c. n = 3, ms = +1/2: 3s, 3p and 3d orbitals all have n = 3. These nine orbitals can each hold
one electron with ms = +1/2; 9 electrons can have these quantum numbers
d. n = 2, ℓ = 2: This combination is not possible (ℓ ≠ 2 for n = 2). Zero electrons in an
atom can have these quantum numbers.
e. n = 1, ℓ = 0, mℓ = 0: These define a 1s orbital which can hold 2 electrons.
CHAPTER 7
67.
ATOMIC STRUCTURE AND PERIODICITY
219
a. Na: 1s22s22p63s1; Na has 1 unpaired electron.
or
1s
2s
2p
3s
3s
b. Co: 1s22s22p63s23p64s23d7; Co has 3 unpaired electrons.
1s
2s
2p
3s
3p
or
4s
3d
2
2
6
2
6
3d
2
10
6
c. Kr: 1s 2s 2p 3s 3p 4s 3d 4p ; Kr has 0 unpaired electrons.
1s
2s
4s
68.
2p
3s
3d
3p
4p
The two exceptions are Cr and Cu.
Cr: 1s22s22p63s23p64s13p5; Cr has 6 unpaired electrons.
1s
2s
2p
3p
or
or
4s
3s
4s
3d
3d
Cu: 1s22s22p63s23p64s13d10; Cu has 1 unpaired electron.
1s
2s
2p
or
4s
4s
3d
3s
3p
220
69.
CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
Si: 1s22s22p63s23p2 or [Ne]3s23p2; Ga: 1s22s22p63s23p64s23d104p1 or [Ar]4s23d104p1
As: [Ar]4s23d104p3; Ge: [Ar]4s23d104p2; Al: [Ne]3s23p1; Cd: [Kr]5s24d10
S: [Ne]3s23p4; Se: [Ar]4s23d104p4
70.
Cu: [Ar]4s23d9 (using periodic table), [Ar]4s13d10 (actual)
O: 1s22s22p4; La: [Xe]6s25d1; Y: [Kr]5s24d1; Ba: [Xe]6s2
Tl: [Xe]6s24f145d106p1; Bi: [Xe]6s24f145d106p3
71.
The following are complete electron configurations. Noble gas shorthand notation could also
be used.
Sc: 1s22s22p63s23p64s23d1; Fe: 1s22s22p63s23p64s23d6
P:
1s22s22p63s23p3; Cs: 1s22s22p63s23p64s23d104p65s24d105p66s1
Eu: 1s22s22p63s23p64s23d104p65s24d105p66s24f65d1*
Pt: 1s22s22p63s23p64s23d104p65s24d105p66s24f145d8*
Xe: 1s22s22p63s23p64s23d104p65s24d105p6; Br: 1s22s22p63s23p64s23d104p5
*
Note: These electron configurations were predicted using only the periodic table.
The actual electron configurations are: Eu: [Xe]6s24f7 and Pt: [Xe]6s14f145d9
72.
Cl: ls22s22p63s23p5 or [Ne]3s23p5
Sb: [Kr]5s24d105p3
Sr: 1s22s22p63s23p64s23d104p65s2 or [Kr]5s2
W: [Xe]6s24f145d4
Pb: [Xe]6s24f145d106p2
Cf: [Rn]7s25f10
Predicting electron configurations for lanthanide and actinide elements is difficult since they
have 0, 1 or 2 electrons in d orbitals.
73.
a. Both In and I have one unpaired 5p electron, but only the nonmetal I would be expected
to form a covalent compound with the nonmetal F. One would predict an ionic
compound to form between the metal In and the nonmetal F.
I: [Kr]5s24d105p5
↑↓ ↑↓ ↑
5p
b. From the periodic table, this will be element 120. Element 120: [Rn]7s25f146d107p68s2
c. Rn: [Xe]6s24f145d106p6; Note that the next discovered noble gas will also have 4f
electrons (as well as 5f electrons).
CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
221
d. This is chromium, which is an exception to the predicted filling order. Cr has 6 unpaired
electrons and the next most is 5 unpaired electrons for Mn.
Cr: [Ar]4s13d5 ↑ ↑ ↑ ↑ ↑ ↑
4s
3d
74.
a. As: 1s22s22p63s23p64s23d104p3
b. Element 116 will be below Po in the periodic table: [Rn]7s25f146d107p4
c. Ta: [Xe]6s24f145d3 or Ir: [Xe]6s24f145d7
d. At: [Xe]6s24f145d106p5. Note that element 117 (when it is discovered) will also have
electrons in the 6p atomic orbitals (as well as electrons in the 7p
atomic orbitals).
75.
Hg: 1s22s22p63s23p64s23d104p65s24d105p66s24f145d10
a. From the electron configuration for Hg, we have 3s2, 3p6, and 3d10 electrons; 18 total
electrons with n = 3.
b. 3d10, 4d10, 5d10; 30 electrons are in d atomic orbitals.
c. 2p6, 3p6, 4p6, 5p6; Each set of np orbitals contain one pz atomic orbital. Because we have
4 sets of np orbitals and two electrons can occupy the pz orbital, there are 4(2) = 8
electrons in pz atomic orbitals.
d. All the electrons are paired in Hg, so one-half of the electrons are spin-up (ms= +1/2) and
the other half are spin-down (ms= 1/2). 40 electrons have spin-up.
76.
Element 115, Uup, is in Group 5A under Bi (bismuth):
Uup: 1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p67s25f146d107p3
a. 5s2, 5p6, 5d10, and 5f14; 32 electrons have n = 5 as one of their quantum numbers
b. ℓ = 3 are f orbitals. 4f14 and 5f14 are the f orbitals used. They are all filled so 28 electrons
have ℓ = 3.
c. p, d, and f orbitals all have one of the degenerate orbitals with mℓ = 1. There are 6 orbitals
with mℓ = 1 for the various p orbitals used; there are 4 orbitals with mℓ =1 for the various
d orbitals used; and there are 2 orbitals with mℓ = 1 for the various f orbitals used. We
have a total of 6 + 4 + 2 = 12 orbitals with mℓ = 1. Eleven of these orbitals are filled with
2 electrons, and the 7p orbitals are only half-filled. The number of electrons with mℓ = 1
is 11 × (2 e) + 1 × (1 e) = 23 electrons.
d. The first 112 electrons are all paired; one-half of these electrons (56 e) will have ms =
1/2. The 3 electrons in the 7p orbitals singly occupy each of the three degenerate 7p
orbitals; the three electrons are spin parallel, so the 7p electrons either have ms = +1/2 or
ms = 1/2. Therefore, either 56 electrons have ms = 1/2 or 59 electrons have ms = 1/2.
222
77.
CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
B: 1s22s22p1
1s
1s
2s
2s
2p*
n
ℓ
mℓ
ms
1
1
2
2
2
0
0
0
0
1
0
0
0
0
1
+1/2
1/2
+1/2
1/2
+1/2
*This is only one of several possibilities for the 2p electron. The 2p electron in B cold have
mℓ = 1, 0 or +1, and ms = +1/2 or 1/2, for a total of six possibilities.
N: 1s22s22p3
1s
1s
2s
2s
2p
2p
2p
78.
n
ℓ
mℓ
ms
1
1
2
2
2
2
2
0
0
0
0
1
1
1
0
0
0
0
-1
0
+1
+1/2
1/2
+1/2
1/2
+1/2
+1/2
+1/2
Ti : [Ar]4s23d2
n ℓ mℓ
(Or all 2p electrons could have ms = 1/2.)
ms
4s
4
0
0 +1/2
4s
4
0
0 1/2
3d
3
2
2 +1/2
3d
3
2
1 +1/2
Only one of 10 possible combinations of mℓ and ms for the first d
electron. For the ground state, the second d electron should be in
a different orbital with spin parallel; 4 possibilities.
79.
O: 1s22s22px22py2 (↑↓ ↑↓ ); There are no unpaired electrons in this oxygen atom. This
configuration would be an excited state, and in going to the more stable ground state
(↑↓ ↑ ↑ ), energy would be released.
80.
The number of unpaired electrons is in parentheses.
a. excited state of boron
B ground state: 1s22s22p1
(1)
(1)
b. ground state of neon
Ne ground state: 1s22s22p6
(0)
CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
c. exited state of fluorine
F ground state: 1s22s22p5
(3)
d. excited state of iron
223
(6)
Fe ground state: [Ar]4s23d6 (4)
(1)
↑↓ ↑↓ ↑
2p
↑↓ ↑ ↑ ↑ ↑
3d
81.
None of the s block elements have 2 unpaired electrons. In the p block, the elements with
either ns2np2 or ns2np4 valence electron configurations have 2 unpaired electrons. For
elements 1-36, these are elements C, Si, and Ge (with ns2np2), and element O, S, and Se (with
ns2np4). For the d block, the elements with configurations nd2 or nd8 have two unpaired
electrons. For elements 1-36, these are Ti (3d2) and Ni (3d8). A total of 8 elements from the
first 36 elements have two unpaired electrons in the ground state.
82.
The s block elements with ns1 for a valence electron configuration have one unpaired
electrons. These are elements H, Li, Na, and K for the first 36 elements. The p block elements
with ns2np1 or ns2np5 valence electron configurations have one unpaired electron. These are
elements B, Al, and Ga (ns2np1) and elements F, Cl, and Br (ns2np5 ) for the first 36 elements.
In the d block, Sc ([Ar]4s23d1) and Cu ([Ar]4s13d10) each have one unpaired electron. A total
of 12 elements from the first 36 elements have one unpaired electron in the ground state.
83.
We get the number of unpaired electrons by examining the incompletely filled subshells. The
paramagnetic substances have unpaired electrons, and the ones with no unpaired electrons are
not paramagnetic (they are called diamagnetic).
Li: 1s22s1 ↑ ; Paramagnetic with 1 unpaired electron.
2s
N: 1s22s22p3 ↑ ↑ ↑ ; Paramagnetic with 3 unpaired electrons.
2p
Ni: [Ar]4s23d8 ↑↓ ↑↓ ↑↓ ↑ ↑ ; Paramagnetic with 2 unpaired electrons.
3d
Te: [Kr]5s24d105p4 ↑↓ ↑ ↑ ; Paramagnetic with 2 unpaired electrons.
5p
Ba: [Xe]6s2 ↑↓ ; Not paramagnetic since no unpaired electrons.
6s
84.
Hg: [Xe]6s24f145d10 ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ; Not paramagnetic since no unpaired electrons.
5d
We get the number of unpaired electrons by examining the incompletely filled subshells.
O: [He]2s22p4
2p4:
↑↓ ↑ ↑
two unpaired e
O+: [He]2s22p3
2p3:
↑
three unpaired e
O: [He]2s22p5
2p5:
↑↓ ↑↓ ↑
Os: [Xe]6s24f145d6
5d6:
↑↓ ↑ ↑ ↑
↑
↑
one unpaired e
↑
four unpaired e
224
CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
Zr: [Kr]5s24d2
4d2:
↑
↑
two unpaired e
S: [Ne]3s23p4
3p4:
↑↓ ↑ ↑
two unpaired e
F: [He]2s22p5
2p5:
↑↓ ↑↓ ↑
one unpaired e
Ar: [Ne]3s23p6
3p6
↑↓ ↑↓ ↑↓
zero unpaired e
The Periodic Table and Periodic Properties
85.
Size (radii) decreases left to right across the periodic table, and size increases from top to
bottom of the periodic table.
a. S < Se < Te
b. Br < Ni < K
c. F < Si < Ba
86.
a. Be < Na < Rb
b. Ne < Se < Sr
c. O < P < Fe; All follow the general
radii trend.
87.
The ionization energy trend is the opposite of the radii trend; ionization energy (IE), in
general, increases left to right across the periodic table and decreases from top to bottom of
the periodic table.
a. Te < Se < S
b. K < Ni < Br
c. Ba < Si < F
88.
a. Rb < Na < Be
b. Sr < Se < Ne
c. Fe < P < O ; All follow the general IE
trend.
89.
a. He
b. Cl
c. Element 117 is the next halogen to be discovered (under At), element 119 is the next
alkali metal to be discovered (under Fr), and element 120 is the next alkaline earth metal
to be discovered (under Ra). From the general radii trend, the halogen (element 117) will
be the smallest.
d. Si
e. Na+. This ion has the fewest electrons as compared to the other sodium species present.
Na+ has the smallest amount of electron-electron repulsions, which makes it the smallest
ion with the largest ionization energy.
90.
a.
Ba
b.
K
c. O; In general, group 6A elements have a lower ionization energy than neighboring group
5A elements. This is an exception to the general ionization energy trend across the
periodic table.
CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
225
d. S2; This ion has the most electrons as compared to the other sulfur species present. S2
has the largest amount of electron-electron repulsions which leads to S2 having the
largest size and smallest ionization energy.
e. Cs; This follows the general ionization energy trend.
91.
a. Sg: [Rn]7s25f146d4
92.
a. Uus will have 117 electrons. [Rn]7s25f146d107p5
b. W
c. SgO3 or Sg2O3 and SgO42 or Sg2O72
(similar to Cr; Sg = 106)
b. It will be in the halogen family and most similar to astatine, At.
c. Uus should form -1 charged anions like the other halogens.
NaUus, Mg(Uus)2, C(Uus)4, O(Uus)2
d. Assuming Uus is like the other halogens: UusO-, UusO2-, UusO3-, UusO493.
As: [Ar]4s23d104p3; Se: [Ar]4s23d104p4; The general ionization energy trend predicts that Se
should have a higher ionization energy than As. Se is an exception to the general ionization
energy trend. There are extra electron-electron repulsions in Se because two electrons are in
the same 4p orbital, resulting in a lower ionization energy for Se than predicted.
94.
Expected order from IE trend: Be < B < C < N < O
B and O are exceptions to the general IE trend. The IE of O is lower because of the extra
electron-electron repulsions present when two electrons are paired in the same orbital. This
makes it slightly easier to remove an electron from O as compared to N. B is an exception
because of the smaller penetrating ability of the 2p electron in B as compared to the 2s
electrons in Be. The smaller penetrating ability makes it slightly easier to remove an electron
from B as compared to Be. The correct IE ordering taking into account the two exceptions is:
B < Be < C < O < N.
95.
a. More favorable EA: C and Br; The electron affinity trend is very erratic. Both N and Ar
have positive EA values (unfavorable) due to their electron configurations (see text for
detailed explanation).
b. Higher IE: N and Ar (follows the IE trend)
c. Larger size: C and Br (follows the radii trend)
96.
a. More favorable EA: K and Cl; Mg has a positive EA value, and F has a more positive
EA value than expected from its position relative to Cl.
b. Higher IE: Mg and F
c. Larger radius: K and Cl
226
97.
CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
Al(44), Si(120), P(74), S(200.4), Cl(348.7); Based on the increasing nuclear charge,
we would expect the electron affinity (EA) values to become more exothermic as we go from
left to right in the period. Phosphorus is out of line. The reaction for the EA of P is:
P(g) + e → P(g)
[Ne]3s23p3
[Ne]3s23p4
The additional electron in P- will have to go into an orbital that already has one electron.
There will be greater repulsions between the paired electrons in P-, causing the EA of P to be
less favorable than predicted based solely on attractions to the nucleus.
98.
Electron-electron repulsions are much greater in O- than in S- because the electron goes into a
smaller 2p orbital vs. the larger 3p orbital in sulfur. This results in a more favorable (more
exothermic) EA for sulfur.
99.
The electron affinity trend is very erratic. In general, EA becomes more positive in going
down a group and EA becomes more negative from left to right across a period (with many
exceptions).
a. I < Br < F < Cl; Cl is most exothermic (F is an exception).
b. N < O < F; F is most exothermic.
100.
O; The electron-electron repulsions will be much more severe for O + e → O2 than for
O + e → O.
101.
a. Se3+(g) → Se4+(g) + e
b. S(g) + e → S2(g)
c. Fe3+(g) + e → Fe2+(g)
d. Mg(g) → Mg+(g) + e
102.
a. The electron affinity of Mg2+ is ΔH for Mg2+(g) + e → Mg+(g). This is just the reverse
of the second ionization energy for Mg, or EA(Mg2+) = IE2(Mg) = 1445 kJ/mol (Table
7.5).
b. IE of Cl is ΔH for Cl(g) → Cl(g) + e. IE(Cl ) = EA(Cl) = 348.7 kJ/mol (Table 7.7)
c. Cl+(g) + e → Cl(g)
ΔH = IE1(Cl) = 1255 kJ/mol = EA(Cl+)
d. Mg(g) → Mg(g) + e
ΔH = EA(Mg) = 230 kJ/mol = IE(Mg )
Alkali Metals
103.
It should be potassium peroxide, K2O2; stable ionic compounds of potassium have K+ ions,
not K2+ ions.
104.
a. Li3N; lithium nitride
b. NaBr; sodium bromide
c. K2S; potassium sulfide
CHAPTER 7
105.
ATOMIC STRUCTURE AND PERIODICITY
227
c 2.9979  10 8 m / s

= 6.582 × 1014 s 1
λ
455 .5  10 9 m
ν=
E = hν = 6.6261 × 10 34 J s × 6.582 × 1014 s 1 = 4.361 × 10 19 J
106.
For 589.0 nm: ν =
c 2.9979  10 8 m / s
= 5.090 × 1014 s 1

λ
589.0  10 9 m
E = hν = 6.6261 × 10 34 J s × 5.090 × 1014 s 1 = 3.373 × 10 19 J
For 589.6 nm: ν = c/λ = 5.085 × 1014 s 1 ; E = hν = 3.369 × 10 19 J
The energies in kJ/mol are:
3.373 × 10 19 J ×
1 kJ
6.0221  10 23

= 203.1 kJ/mol
1000 J
mol
3.369 × 10 19 J ×
1 kJ
6.0221  10 23

= 202.9 kJ/mol
1000 J
mol
107.
Yes; the ionization energy general trend is to decrease down a group, and the atomic radius
trend is to increase down a group. The data in Table 7.8 confirm both of these general trends.
108.
It should be element #119 with the ground state electron configuration: [Rn]7s25f146d107p68s1
109.
a. 6 Li(s) + N2(g) → 2 Li3N(s)
b. 2 Rb(s) + S(s) → Rb2S(s)
110.
a. 2 Cs(s) + 2 H2O(l) → 2 CsOH(aq) + H2(g)
b. 2 Na(s) + Cl2(g) → 2 NaCl(s)
Additional Exercises
111.
112.
E=
310 kJ
1 mol
= 5.15 × 10 22 kJ = 5.15 × 10 19 J

23
mol
6.022  10
E =
6.626  10 34 J s  2.998  10 8 m / s
hc
hc
=
= 3.86 × 10 7 m = 386 nm
, λ
5.15  10 19 J
E
λ
Energy to make water boil = s × m × ΔT =
Ephoton =
4.18 J
× 50.0 g × 75.0°C = 1.57 × 104 J
g C
hc 6.626  10 34 J s  2.998  10 8 m / s

= 2.04 × 1024 J
λ
9.75  10  2 m
228
CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
1.57 × 104 J ×
1 sec
1 photon
= 20.9 sec; 1.57 × 104 J ×
= 7.70 × 1027 photons
 24
750 . J
2.04  10 J
113.
60 × 106 km ×
1000 m
1s
= 200 s (about 3 minutes)

km
3.00  10 8 m
114.
λ=
100 cm
hc 6.626  10 34 J s  2.998  10 8 m / s

= 5.53 × 10 7 m ×
= 5.53 × 10 5 cm
19
E
3.59  10 J
m
From the spectrum, λ = 5.53 × 10 5 cm is greenish-yellow light.
115.
 1
1 
1 
 1
ΔE = RH  2  2  = 2.178 × 10 18 J  2  2  = -4.840 × 10 19 J
6 
ni 
2
 nf
λ=
6.6261  10 34 J s  2.9979  10 8 m / s
100 cm
hc
= 4.104 × 10 7 m ×

19
| ΔE |
m
4.840  10 J
= 4.104 × 10 5 cm
From the spectrum, λ = 4.104 × 10 5 cm is violet light, so the n = 6 to n = 2 visible spectrum
line is violet.
116.
Exceptions: Cr, Cu, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Pt, Au; The elements Tc, Ru, Rh, Pd and Pt
do not correspond to the supposed extra stability of half-filled and filled subshells.
117.
a. True for H only.
118.
n = 5; mℓ = -4, -3, -2, -1, 0, 1, 2, 3, 4; 18 electrons
119.
When the p and d orbital functions are evaluated at various points in space, the results
sometimes have positive values and sometimes have negative values. The term phase is often
associated with the + and  signs. For example, a sine wave has alternating positive and
negative phases. This is analogous to the positive and negative values (phases) in the p and d
orbitals.
120.
He: 1s2; Ne: 1s22s22p6; Ar: 1s22s22p63s23p6; Each peak in the diagram corresponds to a
subshell with different values of n. Corresponding subshells are closer to the nucleus for
heavier elements because of the increased nuclear charge.
121.
The general ionization energy trend is for ionization energy to increase going left to right
across the periodic table. However, one of the exceptions to this trend occurs between groups
2A and 3A. Between these two groups, group 3A elements usually have a lower ionization
energy than group 2A elements. Therefore, Al should have the lowest first ionization energy
value, followed by Mg, with Si having the largest ionization energy. Looking at the values
for the first ionization energy in the graph, the green plot is Al, the blue plot is Mg, and the
red plot is Si.
b. True for all atoms.
c. True for all atoms.
CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
229
Mg (the blue plot) is the element with the huge jump between I2 and I3. Mg has two valence
electrons, so the third electron removed is an inner core electron. Inner core electrons are
always much more difficult to remove compared to valence electrons since they are closer to
the nucleus, on average, than the valence electrons.
122.
a. The 4+ ion contains 20 electrons. Thus, the electrically neutral atom will contain 24
electrons. The atomic number is 24.
b. The ground state electron configuration of the ion must be: 1s22s22p63s23p64s03d2; There
are 6 electrons in s orbitals.
c. 12
d. 2
e. From the mass, this is the isotope
f.
50
24 Cr.
There are 26 neutrons in the nucleus.
1s22s22p63s23p64s13d5 is the ground state electron configuration for Cr.
exception to the normal filling order.
Cr is an
123.
Valence electrons are easier to remove than inner core electrons. The large difference in
energy between I2 and I3 indicates that this element has two valence electrons. This element
is most likely an alkaline earth metal since alkaline earth metal elements all have two valence
electrons.
124.
All oxygen family elements have ns2np4 valence electron configurations, so this nonmetal is
from the oxygen family.
a. 2 + 4 = 6 valence electrons
b. O, S, Se and Te are the nonmetals from the oxygen family (Po is a metal).
c. Because oxygen family nonmetals form -2 charged ions in ionic compounds, K2X would
be the predicted formula where X is the unknown nonmetal.
d. From the size trend, this element would have a smaller radius than barium.
e. From the ionization energy trend, this element would have a smaller ionization energy
than fluorine.
125.
a.
Na(g) → Na+(g) + e
IE1 = 495 kJ


Cl(g) + e → Cl (g)
EA = 348.7 kJ
______________________________________________
Na(g) + Cl(g) → Na+(g) + Clg)
ΔH = 146 kJ
b.
Mg(g) → Mg+(g) + e
IE1 = 735 kJ
F(g) + e→ F-(g)
EA = 327.8 kJ
_____________________________________________
Mg(g) + F(g) → Mg+(g) + F(g)
ΔH = 407 kJ
230
CHAPTER 7
c.
ATOMIC STRUCTURE AND PERIODICITY
Mg+(g) → Mg2+(g) + e
IE2 = 1445 kJ
F(g) + e  → F(g)
EA = 327.8 kJ
______________________________________________
Mg+(g) + F(g) → Mg2+(g) + F(g)
ΔH = 1117 kJ
d. From parts b and c we get:
Mg(g) + F(g) → Mg+(g) + F(g)
ΔH = 407 kJ
+
2+

Mg (g) + F(g) → Mg (g) + F (g)
ΔH = 1117 kJ
______________________________________________
Mg(g) + 2 F(g) → Mg2+(g) + 2 F(g)
ΔH = 1524 kJ
Challenge Problems
126.
Ephoton =
hc 6.6261  10 34 J s  2.9979  10 8 m / s

= 7.839 × 10 19 J; ΔE = 7.839 × 10 19 J
λ
253 .4  10 9 m
The general energy equation for one-electron ions is En = 2.178 × 10 18 J (Z2)/n2
where Z = atomic number.
 1
1
ΔE = 2.178 × 10 18 J (Z)2  2  2
ni
 nf

 , Z = 4 for Be3+


 1
1 
ΔE = 7.839 × 10 19 J = 2.178 × 10 18 (4)2  2  2 
 nf 5 
7.839  10 19
2.178  10
18
 16

1
1
1
= 2 , 2 = 0.06249, nf = 4
25
nf nf
This emission line corresponds to the n = 5 → n = 4 electronic transition.
127.
a. Because wavelength is inversely proportional to energy, the spectral line to the right of B
(at a longer wavelength) represents the lowest possible energy transition; this is n = 4 to n
= 3. The B line represents the next lowest energy transition, which is n = 5 to n = 3 and
the A line corresponds to the n = 6 to n = 3 electronic transition.
b. This spectrum is for a one-electron ion, thus En = -2.178 × 10-18 J (Z2/n2). To determine
ΔE and, in turn, the wavelength of spectral line A, we must determine Z, the atomic
number of the one-electron species. Use spectral line B data to determine Z.
 Z2 Z2 
1
1
ΔE5 → 3 = 2.178 × 10 18 J (Z)2  2  2  = 2.178 × 10 18 J  2  2 
5 
5 
3
3
 16 Z 2 

ΔE5 →3 = 2.178 × 10-18 

 9  25 
CHAPTER 7
E=
ATOMIC STRUCTURE AND PERIODICITY
231
hc 6.6261  10 34 J s  2.9979  10 8 m / s
= 1.394 × 10 18 J

λ
142 .5  10 9 m
Because an emission occurs, ΔE5 → 3 = 1.394 × 10 18 J.
 16 Z 2 
 , Z2 = 9.001, Z = 3; The ion is Li2+.
ΔE = 1.394 × 10 18 J = -2.178 × 10 18 J 

9

25


Solving for the wavelength of line A:
1 
1
ΔE6 → 3 = 2.178 × 10 18 (3)2  2  2  = 1.634 × 10 18 J
6 
3
λ
128.

6.6261  10 34 J s  2.9979  10 8 m / s
hc
= 1.216 × 10 7 m = 121.6 nm

18
| ΔE |
1.634  10 J
1
 1
For hydrogen: ΔE = 2.178 × 10-18 J  2  2  = 4.574 × 10 19 J
5 
2
For a similar blue light emission, He+ will need about the same ΔE value.
For He+: En = 2.178 × 10 18 J (Z2/n2) where Z = 2:
 22 22 
ΔE = 4.574 × 10 19 J = 2.178 × 10-18 J  2  2 
 nf 4 
0.2100 =
4
4
4
 , 0.4600 = 2 , nf = 2.949
2
nf 16
nf
The transition from n = 4 to n = 3 for He+ should emit similar colored blue light as the n
= 5 to n = 2 hydrogen transition; both these transitions correspond to very nearly the
same energy change.
129.
For r = ao and θ = 0° (Z = 1 for H):
ψ 2pz =
1
4(2π)1/ 2


1


 5.29  10 11 


3/ 2
(1) e1/2 cos 0 = 1.57 × 1014; ψ2 = 2.46 × 1028
For r = ao and θ = 90°, ψ 2 p z = 0 since cos 90° = 0; ψ2 = 0
There is no probability of finding an electron in the 2pz orbital with θ = 0°. As expected, the
xy plane, which corresponds to θ = 0°, is a node for the 2pz atomic orbital.
232
130.
CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
a. Each orbital could hold 3 electrons.
b. The first period corresponds to n = 1 which can only have 1s orbitals. The 1s orbital
could hold 3 electrons, hence the first period would have three elements. The second
period corresponds to n = 2, which has 2s and 2p orbitals. These four orbitals can each
hold three electrons. A total of 12 elements would be in the second period.
c. 15
131 .
d. 21
a. 1st period:
p = 1, q = 1, r = 0, s = ± 1/2 (2 elements)
2nd period:
p = 2, q = 1, r = 0, s = ± 1/2 (2 elements)
3rd period:
p = 3, q = 1, r = 0, s = ± 1/2 (2 elements)
p = 3, q = 3, r = -2, s = ± 1/2 (2 elements)
p = 3, q = 3, r = 0, s = ± 1/2 (2 elements)
p = 3, q = 3, r = +2, s = ± 1/2 (2 elements)
4th period:
p = 4; q and r values are the same as with p = 3 (8 total elements)
1
2
3
4
5
6
7
8
9 10 11 12
13 14 15 16 17 18 19 20
b. Elements 2, 4, 12 and 20 all have filled shells and will be least reactive.
c. Draw similarities to the modern periodic table.
XY could be X+Y, X2+Y2 or X3+Y3. Possible ions for each are:
X+ could be elements 1, 3, 5 or 13; Y could be 11 or 19.
X2+ could be 6 or 14; Y2 could be 10 or 18.
X3+ could be 7 or 15; Y3 could be 9 or 17.
Note: X4+ and Y4 ions probably won’t form.
XY2 will be X2+(Y )2; See above for possible ions.
X2Y will be (X+)2Y2 See above for possible ions.
XY3 will be X3+(Y )3; See above for possible ions.
X2Y3 will be (X3+)2(Y2 )3; See above for possible ions.
CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
233
d. p = 4, q = 3, r = 2 , s = ± 1/2 (2)
p = 4, q = 3, r = 0, s = ± 1/2 (2)
p = 4, q = 3, r = +2, s = ± 1/2 (2)
A total of 6 electrons can have p = 4 and q = 3.
e.
p = 3, q = 0, r = 0: This is not allowed; q must be odd. Zero electrons can have these
quantum numbers.
f.
p = 6, q = 1, r = 0, s = ± 1/2 (2)
p = 6, q = 3, r = 2, 0, +2; s = ± 1/2 (6)
p = 6, q = 5, r = 4, -2, 0, +2, +4; s = ± 1/2 (10)
Eighteen electrons can have p = 6.
132.
The third IE refers to the following process: E2+ → E3+ + e
configurations for the +2 charged ions of Na to Ar are:
Na2+:
Mg2+:
1s22s22p5
1s22s22p6
Al2+:
Si2+:
P2+:
S2+:
Cl2+:
Ar2+:
H = IE3. The electron
[Ne]3s1
[Ne]3s2
[Ne]3s23p1
[Ne]3s23p2
[Ne]3s23p3
[Ne]3s23p4
IE3 for sodium and magnesium should be extremely large as compared to the others because
n = 2 electrons are much more difficult to remove than n = 3 electrons. Between Na2+ and
Mg2+, one would expect to have the same trend as seen with IE1(F) versus IE1(Ne); these
neutral atoms have identical electron configurations to Na2+ and Mg2+. Therefore the
1s22s22p5 ion (Na2+) should have a lower ionization energy than the 1s22s22p6 ion (Mg2+).
The remaining 2+ ions (Al2+ to Ar2+) should follow the same trend as the neutral atoms
having the same electron configurations. The general IE trend predicts an increase from
[Ne]3s1 to [Ne]3s23p4. The exceptions occur between [Ne]3s2 to [Ne]3s23p1 and between
[Ne]3s23p3 and [Ne]3s23p4. [Ne]3s23p1 is out of order because of the small penetrating ability
of the 3p electron as compared to the 3s electrons. [Ne]3s23p4 is out of order because of the
extra electron-electron repulsions present when two electrons are paired in the same orbital.
Therefore, the correct ordering for Al2+ to Ar2+ should be Al2+ < P2+ < Si2+ < S2+ < Ar2+ < Cl2+
where P2+ and Ar2+ are out of line for the same reasons that Al and S are out of line in the
general ionization energy trend for neutral atoms.
234
CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
IE
Na2+
Mg2+
Al2+
Si2+
P2+
S2+
Cl2+
Ar2+
Note: The actual numbers in Table 7.5 support most of this plot. No IE3 is given for Na2+, so
you cannot check this. The only deviation from our discussion is IE3 for Ar2+ which is greater
than IE3 for Cl2+ instead of less than.
133.
The ratios for Mg, Si, P, Cl, and Ar are about the same. However, the ratios for Na, Al, and S
are higher. For Na, the second IE is extremely high because the electron is taken from n = 2
(the first electron is taken from n = 3). For Al, the first electron requires a bit less energy than
expected due to the fact it is a 3p electron versus a 3s electron. For S, the first electron
requires a bit less energy than expected due to electrons being paired in one of the p orbitals.
134.
Size also decreases going across a period. Sc & Ti and Y & Zr are adjacent elements. There
are 14 elements (the lanthanides) between La and Hf, making Hf considerable smaller.
135.
a. As we remove succeeding electrons, the electron being removed is closer to the nucleus,
and there are fewer electrons left repelling it. The remaining electrons are more strongly
attracted to the nucleus, and it takes more energy to remove these electrons; successive
ionization energies should increase.
b. Al : 1s22s22p63s23p1; For I4, we begin by removing an electron with n = 2. For I3, we
remove an electron with n = 3. In going from n = 3 to n = 2, there is a big jump in
ionization energy because the n = 2 electrons (inner core electrons) are much closer to the
nucleus on average than n = 3 electrons (valence electrons). Since the n = 2 electrons are
closer to the nucleus, they are held more tightly and require a much larger amount of
energy to remove them compared to the n = 3 electrons.
c. Al4+; The electron affinity for Al4+ is ΔH for the reaction:
Al4+(g) + e →Al3+(g)
ΔH = I4 = -11,600 kJ/mol
CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
235
d. The greater the number of electrons, the greater the size.
Size trend: Al4+ < Al3+ < Al2+ < Al+ < Al
136.
None of the noble gases and no subatomic particles had been discovered when Mendeleev
published his periodic table. Thus, there was not an element out of place in terms of
reactivity. There was no reason to predict an entire family of elements. Mendeleev ordered
his table by mass; he had no way of knowing there were gaps in atomic numbers (they hadn't
been discovered yet).
137.
m=
h
6.626  10 34 kg m 2 / s

 6.68  10  26 kg / atom
15
8
λv
3.31  10 m  (0.0100  2.998  10 m/s )
6.68  10 26 kg
6.022  10 23 atoms
1000 g


= 40.2 g/mol
atom
1 mol
1 kg
The element is calcium, Ca.
Integrated Problems
138.
a.  =
=
E
7.52  10 19 J

= 1.13 × 1015 s 1
34
h
6.626  10 J s
c
2.998  10 8 m / s

= 2.65 × 10 7 m = 265 nm
ν
1.13  1015 s 1
b. Ephoton and  are inversely related (E = hc/). Any wavelength of EMR less than or equal
to 265 nm (  265) will have sufficient energy to eject an electron. So, yes 259 nm
EMR will eject an electron.
c. This is the electron configuration for copper, Cu, an exception to the expected filling
order.
139.
a. An atom of francium has 87 protons and 87 electrons. Francium is an alkali metal and
forms stable 1+ cations in ionic compounds. This cation would have 86 electrons.
Therefore, the electron configurations will be:
Fr: [Rn]7s1; Fr+: [Rn] = [Xe]6s24f145d106p6
b. 1.0 oz Fr ×
1 lb
1 kg
1000 g
1 mol Fr
6.02  10 23 atoms




16 oz 2.205 lb
1 kg
223 g Fr
1 mol Fr
= 7.7 × 1022 atoms Fr
c.
223
Fr is element 87, so it has 223 – 87 = 136 neutrons.
236
CHAPTER 7
136 neutrons 
140.
ATOMIC STRUCTURE AND PERIODICITY
1.67493  10 27 kg 1000 g

 2.27790  10  22 g neutrons
1 neutron
1 kg
a. [Kr]5s24d105p6 = Xe; [Kr]5s24d105p1 = In; [Kr]5s24d105p3 = Sb
From the general radii trend, the increasing size order is Xe < Sb < In.
b. [Ne]3s23p5 = Cl; [Ar]4s23d104p3 = As; [Ar]4s23d104p5 = Br
From the general IE trend, the decreasing IE order is: Cl > Br > As.
Marathon Problem
141.
a. Let λ = wavelength corresponding to the energy difference between the excited state,
n = ?, and the ground state, n = 1. Use the information in part a to first solve for the
energy difference, ΔE1 → n, and then solve for the value of n. From the problem, λ =
(λradio/3.00 × 107).
ΔE1 → n =
λradio =
hc
hc
hc  3.00  10 7

,
λ

radio
λ
ΔE1  n
(λ radio / 3.00  10 7 )
c
ν radio

c
; Equating the two λradio expressions gives:
97.1  10 6 s 1
hc  3.00  10 7
c
=
, ΔE1 → n = h × 3.00 × 107 × 97.1 × 106
ΔE1  n
97.1  10 6 s 1
ΔE1 → n = 6.626 × 10 34 J s × 3.00×107 × 97.1×106 s 1 = 1.93 × 10 18 J
Now we can solve for the n value of the excited state.
1
 1
ΔE1 → n = 1.93 × 10 18 J = 2.178 × 10 18  2  2 
1 
n
1
 1.93  10 18  2.178  10 18

= 0.11, n = 3 = energy level of the excited state
2
n
2.178  10 18
b. From de Broglie’s equation:
λ=
h
6.626  10 34 J s

 1.28  10 6 m
31
mv
9.109  10 kg  570 . m / s
Let n = V = principal quantum number of the valence shell of element X. The electronic
transition in question will be from n = V to n = 3 (as determined in part a).
CHAPTER 7
ATOMIC STRUCTURE AND PERIODICITY
237
1 
1
ΔEn → 3 = 2.178 × 10 18  2  2 
n 
3
|ΔEn → 3| =
hc
6.626  10 34 J s  2.998  10 8 m / s

 1.55  10 19 J
λ
1.28  10 6 m
1 1 
ΔEn → 3 = 1.55 × 10 19 J = 2.178 × 10 18 J   2 
9 n 
1
 1.55  10 19  2.178  10 18  
1
 9  = 0.040, n = 5

2
6
n
1.28  10 m
Thus, V = 5 = the principal quantum number for the valence shell of element X, that is,
element X is in the fifth period (row) of the periodic table (element X = Rb  Xe).
c. For n = 2, we can have 2s and 2p orbitals. None of the 2s orbitals have mℓ = 1 and only
one of the 2p orbitals has mℓ = 1. In this one 2p atomic orbital, only one electron can
have ms = 1/2. Thus, only one unpaired electron exists in the ground state for element X.
From period 5 elements, X could be Rb, Y, Ag, In or I since all of these elements only
have one unpaired electron in the ground state.
d. Element 120 will be the next alkaline earth metal discovered. Alkaline earth metals form
2+ charged ions in stable ionic compounds.
Thus, the angular momentum quantum number (ℓ) for the subshell of X which contains
the unpaired electron is 2, which means the unpaired electron is in the d subshell.
Although Y and Ag are both d-block elements, only Y has one unpaired electron in the dblock. Silver is an exception to the normal filling order; Ag has the unpaired electron in
the 5s orbital. The ground state electron configurations are:
Y: [Kr]5s24d1 and Ag: [Kr]5s14d10
Element X is yttrium (Y).