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Modern Atomic Theory
Review
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11 | 1
QUESTION
The concept of the nuclear atom left unanswered questions about
1. why the nucleus is so dense.
2. why the negative electrons do not collapse into the
positive nucleus.
3. what isotopes are.
4. the mass of the nucleus.
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11 | 2
ANSWER
Choice #2 properly explains that the nuclear atom did not explain
the stable position of electrons relative to the positive nucleus.
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11 | 3
QUESTION
The relationship between the wavelength and frequency of
radiation is expressed by the equation:
1.
2.
3.
4.
λν = c
λ = 1/ν
ν = cλ
ν = 1/c + λ
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11 | 4
ANSWER
Choice #1 provides the correct relationship:
Wavelength (λ) × frequency (ν) = the speed of light in a vacuum (c)
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11 | 5
QUESTION
The concept of photons emphasizes the particle-like nature of
light rather than its wave-like nature. A photon of infrared light
has more energy in it than a photon of
1.
2.
3.
4.
visible light
ultraviolet light
x-rays
microwave radiation
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ANSWER
Choice #4. X-rays, UV light, and visible radiation are all more
energetic than infrared.
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11 | 7
QUESTION
When the electrons in atoms receive energy from a source, they
go into an excited state but quickly return back to its ground
state by
1.
2.
3.
4.
nuclear fusion.
emitting a photon of light.
emitting a proton.
absorbing heat.
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11 | 8
ANSWER
Choice #2 correctly describes a common mode of relaxation of
excited state atoms.
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11 | 9
QUESTION
The concept that electrons in an atom can only occupy specific
energy levels is equivalent to saying that the energy levels are
1.
2.
3.
4.
varied.
quantized.
superimposed.
continuous.
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11 | 10
ANSWER
Choice #2 reflects the concept that there are specific allowable
energy levels in which electrons can exist.
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11 | 11
QUESTION
Which of the following is true regarding the atom?
1. All atoms of the same element are identical.
2. As verified by Rutherford, only positively charged particles
called protons are found inside the nucleus.
3. Electrons located further from the nucleus have more
predictable behavior because they contain less energy.
4. Electrons display both particle-like behavior (they have mass)
and wave-like behavior (they are associated with probability).
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11 | 12
ANSWER
Choice #4 is the correct answer. Not all atoms of the same
element are identical (due to isotopes and ions). Neutrons are
also found in the nucleus of an atom in addition to protons.
Electrons located further from the nucleus have less predictable
behavior and contain more energy.
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11 | 13
QUESTION
When an electron is excited in an atom or ion
1. only specific quantities of energy are released in order for the
electron to return to its ground state.
2. white light is never observed when the electron returns to its
ground state.
3. the electron is only excited to certain energy levels.
4. All of the above statements are true when an electron is
excited.
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11 | 14
ANSWER
Choice #4 is the correct answer.
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11 | 15
QUESTION
How many of the following statements are true concerning an electron in its
ground state?
I. The electron must be in its lowest-energy state.
II. Energy must be applied to the electron in order to excite
it.
III. The electron must be located on the nucleus of an atom.
IV. The electron can release energy to obtain a lower ground
state.
1. 1
2. 2
3. 3
4. 4
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ANSWER
Choice #2 is the correct answer. I and II are correct.
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11 | 17
QUESTION
The Bohr model of the hydrogen atom explained the emission
spectrum of the hydrogen atom with the concept of
1. quantized energy levels.
2. quantized electron orbits.
3. transitions of electrons from higher to lower energy
levels.
4. all of the above
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ANSWER
Choice #4 reflects the quantized nature of the electron energy
levels and the production of photons of specific energies that
correspond to transitions between quantized levels.
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11 | 19
QUESTION
The atomic model developed by Neils Bohr only works for the
hydrogen atom. Choose the best answer that describes why
this model does not work for other atoms.
1. The hydrogen atom has only one proton. The nuclei of other
atoms would be able to pull the electrons out of their orbits.
2. The hydrogen atom has only one electron. Since other
elements have more than one electron, the repulsions between
electrons cannot be described by this model.
3. Other atoms are larger than hydrogen atoms, so they fill up
too much space to be defined by orbits.
4. Hydrogen is the only element that has quantized energy levels
like those described by this model.
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ANSWER
Choice #2 is the correct answer.
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11 | 21
QUESTION
In the wave mechanical model of the atom, electron orbitals are
probability density diagrams of where the electron is likely to be
found. These maps of where the electron is most likely to be were
developed
1.
2.
3.
4.
from atomic emission spectra.
by Niels Bohr.
by experiments with a cathode ray tube.
from mathematical analyses by Schrödinger.
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11 | 22
ANSWER
Choice #4 presents the idea that electron orbitals are
mathematical descriptions of electron probability densities,
derived from solutions to the Schrödinger equation.
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11 | 23
QUESTION
At the third principal energy level of an atom, the number of
orbitals equals
1.
2.
3.
4.
3
6
9
12
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ANSWER
Choice #3 correctly identifies the sum of the orbitals at that level:
one 3s orbital + three 3p orbitals + five 3d orbitals = nine orbitals.
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11 | 25
QUESTION
The number of electrons that can be accommodated in the n = 2
level is:
1.
2.
3.
4.
2
4
6
8
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11 | 26
ANSWER
Choice #4 correctly predicts that 8 electrons can fit in the n = 2
level. Two electrons fill the 2s orbital and 6 electrons fill the set
of three 2p orbitals.
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11 | 27
QUESTION
Which of the following statements best describes the movement
of electrons in a p orbital?
1. The electron movement cannot be exactly determined.
2. The electrons move within the two lobes of the p orbital, but
never beyond the outside surface of the orbital.
3. The electrons are concentrated at the center (node) of the two
lobes.
4. The electrons move along the outer surface of the p orbital,
similar to a “figure 8” type of movement.
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11 | 28
ANSWER
Choice #1 is the correct answer.
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11 | 29
QUESTION
Write out the electron configuration for an atom of phosphorus
and indicate the number of unpaired electrons
1.
2.
3.
4.
[Ne]3s23p3 ; 3 unpaired electrons
[Ne]2s22p63s23p3 ; 3 unpaired electrons
[Ne]3s23p3 ; 5 unpaired electrons
[Ne]3p5 ; 5 unpaired electrons
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ANSWER
Choice #1 is correct. Each of the three 3p orbitals has one
unpaired electron in it. The electrons in the 3s orbital are paired.
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11 | 31
QUESTION
The number of valence electrons in an atom of Cl is:
1.
2.
3.
4.
7
5
3
1
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ANSWER
Choice #1 is correct. Cl has 2 valence electrons in the 3s orbital
and 5 in the 3p subset.
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QUESTION
How many unpaired electrons does sulfur contain in its ground
state?
1.
2.
3.
4.
0
1
2
3
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ANSWER
Choice #3 is correct. There are 4 electrons in the p orbitals, with
one of the p orbitals containing paired electrons and two of the p
orbitals containing unpaired electrons.
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QUESTION
How many unpaired electrons does the element cobalt (Co) have
in its lowest energy state?
1.
2.
3.
4.
0
2
3
7
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11 | 36
ANSWER
Choice #3 is correct. There are 7 electrons in the d orbitals, with
two of the d orbitals containing paired electrons and three of the d
orbitals containing unpaired electrons.
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11 | 37
QUESTION
Can an electron in a phosphorus atom ever be in a 3d orbital?
Choose the best answer.
1. Yes. An electron can be excited into a 3d orbital.
2. Yes. A ground-state electron in phosphorus is located in a 3d
orbital.
3. No. Only transition metal atoms can have electrons located in
the d orbitals.
4. No. This would not correspond to phosphorus’ electron
arrangement in its ground state.
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11 | 38
ANSWER
Choice #1 is the correct answer.
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11 | 39
QUESTION
The Lanthanides correspond to filling up the ____set of orbitals.
1.
2.
3.
4.
3d
3f
4f
5f
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11 | 40
ANSWER
Choice #3 correctly associates the 14 elements that make up the
lanthanides with 14 available slots for electrons in the set of
seven 4f orbitals.
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11 | 41
QUESTION
Determine the expected electron configuration for the element
Eu.
1.
2.
3.
4.
[Xe]6s24f6
[Rn]7s25f7
[Xe]4f7
[Xe]6s24f7
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11 | 42
ANSWER
Choice #4 is the correct answer.
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11 | 43
QUESTION
Which element would be likely to have the lowest ionization
energy?
1.
2.
3.
4.
Na
Al
Cl
Cs
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11 | 44
ANSWER
Choice #4 should be selected. Ionization energy increases from
left to right, but decreases from top to bottom.
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11 | 45
QUESTION
Which of the following elements has the largest ionization
energy?
1.
2.
3.
4.
P
Al
Cl
K
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11 | 46
ANSWER
Choice #3 is the correct answer. Ionization energy increases from
left to right, but decreases from top to bottom.
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11 | 47
QUESTION
Which of the following elements has the largest ionization
energy?
1.
2.
3.
4.
S
Ba
Cr
Mg
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11 | 48
ANSWER
Choice #1 is the correct answer. Ionization energy increases from
left to right, but decreases from top to bottom.
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11 | 49
QUESTION
Which of the following atoms is likely to have the largest atomic
radius?
1.
2.
3.
4.
Na
Al
Cl
K
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11 | 50
ANSWER
Choice #4. Atomic radius decreases as one proceeds across the
third period, but increases from top to bottom.
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11 | 51
QUESTION
Which of the following atoms is likely to have the largest atomic
radius?
1.
2.
3.
4.
Ca
Sr
N
Al
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11 | 52
ANSWER
Choice #2. Atomic radius decreases as one proceeds across the
third period, but increases from top to bottom.
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11 | 53
QUESTION
Which of the following is ranked in order of largest to smallest
atomic radius?
1.
2.
3.
4.
F > S > Ge > Mn
Mn > Rb > F > S
Rb > Mn > Ge >
Rb > Ge > Mn >
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> Rb
> Ge
S > F
F > S
11 | 54
ANSWER
Choice #3. Atomic radius decreases as one proceeds across the
third period, but increases from top to bottom.
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11 | 55
QUESTION
Rank the following from smallest to largest atomic radius.
1.
2.
3.
4.
O, Zn, Ca, Ba
O, Ca, Zn, Ba
Ba, Ca, Zn, O
O, Zn, Ba, Ca
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11 | 56
ANSWER
Choice #1. Atomic radius decreases as one proceeds across the
third period, but increases from top to bottom.
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11 | 57
QUESTION
Which has a smaller atomic radius, an atom of fluorine or an atom of lithium?
Choose the best answer.
1. They are the same size because their electrons are contained in the same
principle energy level.
2. An atom of lithium is smaller than an atom of fluorine because lithium
has fewer protons.
3. An atom of fluorine is smaller than an atom of lithium because with more
protons the electrons are pulled closer to the nucleus.
4. An atom of fluorine is smaller than an atom of lithium because fluorine
has a high ionization energy and will not lose electrons as easily as lithium.
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11 | 58
ANSWER
Choice #3 is the correct answer.
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11 | 59
QUESTION
Which of the following statements is true?
1. The krypton 1s orbital is larger than the helium 1s orbital
because krypton contains more electrons.
2. The krypton 1s orbital is smaller than the helium 1s orbital
because krypton’s nuclear charge draws the electrons closer.
3. The krypton 1s orbital and helium 1s orbital are the same size
because both s orbitals can only have two electrons.
4. The krypton 1s orbital is larger than the helium 1s orbital
because krypton’s ionization energy is lower so it’s easier to
remove electrons.
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11 | 60
ANSWER
Choice #2 is the correct answer.
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11 | 61