Atomic Structure Fill
in Key
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1. In the box shown, or on a separate piece of paper, draw the electron-dot (Lewis) structure of an
atom of calcium. [1]
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2. In the box shown, or on a separate piece of paper, draw the electron-dot (Lewis) structure of an
atom of chlorine. [1]
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3. Base your answer on the information below.
In the modern model of the atom, each atom is composed of three major subatomic (or fundamental)
particles.
Name the subatomic particles contained in the nucleus of the atom. [1]
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4. Base your answer on the information below.
In the modern model of the atom, each atom is composed of three major subatomic (or fundamental)
particles.
State the charge associated with each type of subatomic particle contained in the nucleus of the
atom. [1]
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5. Base your answer on the information below.
In the modern model of the atom, each atom is composed of three major subatomic (or fundamental)
particles.
What is the net charge of the nucleus? [1]
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6. Base your answer on the electron configuration table:< BR>What is the total number of valence
electrons in an atom of electron configuration X? [1]
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7. Base your answer on the electron configuration table:
Which electron configuration represents the excited state of a calcium atom? [1]
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8. John Dalton was an English scientist who proposed that atoms were hard, indivisible spheres. In
the modern model, the atom has a different internal structure.
a Identify one experiment that led scientists to develop the modern model of the atom. [1]
b Describe this experiment. [1]
c State one conclusion about the internal structure of the atom, based on this experiment. [1]
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9. Base your answer on the data table, which shows three isotopes of neon.
Based on the atomic masses and the natural abundances shown in the data table, on a separate piece
of paper, show a correct numerical setup for calculating the average atomic mass of neon. [1]
The atomic mass of an element is determined by calculating the weighted average of the masses of
each isotope. Multiply the mass of each isotope by the decimal equivalent of its percent abundance,
and then add the products together:
(0.909) x (19.99) + (0.003) x (20.99) + (0.088) x (21.99)
[1 point]
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10. Base your answer on the data table, which shows three isotopes of neon.
Based on natural abundances, the average atomic mass of neon is closest to which whole number?
[1]
Since neon-20 has the greatest abundance, the atomic mass of neon will be closest to the isotopic
mass of this isotope, 20. [1 point]
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11. Base your answer on the diagram shown, which represents an atom of magnesium-26 in the
ground state.
What is the total number of valence electrons in an atom of Mg-26 in the ground state?
Valence electrons are those electrons that occupy the outermost level of an atom. Since the electron
configuration for a ground-state magnesium atom is 2-8-2, the atom has a total of 2 valence
electrons.
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12. Base your answer on the diagram shown, which represents an atom of magnesium-26 in the
ground state.
Copy diagram B on a separate piece of paper and write an appropriate number of electrons in each
shell to represent a Mg-26 atom in an excited state. Your answer may include additional shells.
When an atom becomes excited, one or more electrons are promoted to higher energy levels. Refer
to the accompanying diagrams, which represent two such possibilities.
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13. In the early 1900s, experiments were conducted to determine the structure of the atom. One of
these experiments involved bombarding gold foil with alpha particles. Most alpha particles passed
directly through the foil. Some, however, were deflected at various angles. Based on this alpha
particle experiment, state two conclusions that were made concerning the structure of an atom.
Acceptable conclusions include:




The nucleus is small.
The nucleus is dense.
The nucleus is positively charged.
Most of the atom is empty space.
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14. Base your answer on the information below.
An atom has an atomic number of 9, a mass number of 19, and an electron configuration of 2-6-1.
Explain why the number of electrons in the second and third shells shows that this atom is in an
excited state.
Use the Periodic Table of the Elements. The ground-state electron configuration for the element
whose atomic number is 9 (F) is 2-7. Evidently, one of the electrons in the second energy level
has been promoted to the third energy level, producing the excited state 2-6-1.
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15. Base your answer on the information below.
A thiol is very similar to an alcohol, but a thiol has a sulfur atom instead of an oxygen atom in the
functional group. One of the compounds in a skunk's spray is 2-butene-1-thiol. The formula of this
compound is shown in the accompanying diagram.
Explain, in terms of electron configuration, why oxygen atoms and sulfur atoms form compounds
with similar molecular structures.
Use the Periodic Table of the Elements. Oxygen and sulfur are both located in Group 16 of the table
and have the same number of valence electrons (6). As a result, both elements will form
compounds with similar structures.
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16. Base your answer on the information below.
A glass tube is filled with hydrogen gas at low pressure. An electric current is passed through the
gas, causing it to emit light. This light is passed through a prism to separate the light into the bright,
colored lines of hydrogen's visible spectrum. Each colored line corresponds to a particular
wavelength of light. One of hydrogen's spectral lines is red light with a wavelength of 656
nanometers.
Tubes filled with other gases produce different bright-line spectra that are characteristic of each kind
of gas. These spectra have been observed and recorded.
Explain, in terms of electron energy states and energy changes, how hydrogen's bright-line spectrum
is produced.
The electric current causes the electrons in the hydrogen atoms to rise to higher energy states
(excited states). As these electrons fall back to lower energy states, light energy of specific
wavelengths is released.
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17. Base your answer on the information below.
A glass tube is filled with hydrogen gas at low pressure. An electric current is passed through the
gas, causing it to emit light. This light is passed through a prism to separate the light into the bright,
colored lines of hydrogen's visible spectrum. Each colored line corresponds to a particular
wavelength of light. One of hydrogen's spectral lines is red light with a wavelength of 656
nanometers.
Tubes filled with other gases produce different bright-line spectra that are characteristic of each kind
of gas. These spectra have been observed and recorded.
Explain how the elements present on the surface of a star can be identified using bright-line spectra.
Since each element has its own specific bright-line spectrum, the bright-line spectrum of the star
can be compared with the spectra of known elements.
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18. Base your answer on the information below:
The Balmer series refers to the visible bright lines in the spectrum produced by hydrogen atoms. The
color and wavelength of each line in this series are given in the accompanying table.
Explain, in terms of both subatomic particles and energy states, how the Balmer series is produced.
[1]
Light is emitted when an excited electron drops from a higher-energy electron shell to a lowerenergy electron shell. [1 point]
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19. Base your answer on the accompanying table.
In the space provided or on a separate piece of paper, draw a Lewis electron-dot diagram for an
atom of sulfur-33. [1]
An electron-dot diagram displays the paired and unpaired electrons in the valence level. Refer to the
solution diagram:
[1 point]
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20. Base your answer on the accompanying table.
In the space provided or on a separate piece of paper, show a correct numerical setup for
calculating the atomic mass of sulfur. [1]
The atomic mass of sulfur is the weighted average of its naturally occurring isotopes. Multiply the
mass of each isotope by the decimal equivalent of the abundance, and add the four terms:
(31.97 u)(0.9493) + (32.97 u)(0.0076) +
(33.97 u)(0.0429) + (35.97 u)(0.0002)
[1 point]
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21. Base your answer on the information below.
In 1897, J. J. Thomson demonstrated in an experiment that cathode rays were deflected by an
electric field. This suggested that cathode rays were composed of negatively charged particles found
in all atoms. Thomson concluded that the atom was a positively charged sphere of almost uniform
density in which negatively charged particles were embedded. The total negative charge in the atom
was balanced by the positive charge, making the atom electrically neutral.
In the early 1900s, Ernest Rutherford bombarded a very thin sheet of gold foil with alpha particles.
After interpreting the results of the gold foil experiment, Rutherford proposed a more sophisticated
model of the atom.
State one conclusion from Rutherford's experiment that contradicts one conclusion made by
Thomson. [1]
Either of the two responses shown below is acceptable for credit:


An atom has a positively charged nucleus.
An atom is mostly empty space.
[1 point]
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22. Base your answer on the information below.
In 1897, J. J. Thomson demonstrated in an experiment that cathode rays were deflected by an
electric field. This suggested that cathode rays were composed of negatively charged particles found
in all atoms. Thomson concluded that the atom was a positively charged sphere of almost uniform
density in which negatively charged particles were embedded. The total negative charge in the atom
was balanced by the positive charge, making the atom electrically neutral.
In the early 1900s, Ernest Rutherford bombarded a very thin sheet of gold foil with alpha particles.
After interpreting the results of the gold foil experiment, Rutherford proposed a more sophisticated
model of the atom.
State one aspect of the modern model of the atom that agrees with a conclusion made by Thomson.
[1]
Either of the two responses shown below is acceptable for credit:


All atoms contain electrons.
An atom has equal amounts of positive and negative charges.
[1 point]
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23. Base your answer on the information below.
An atom in an excited state has an electron configuration of 2-7-2.
Explain, in terms of subatomic particles, why this excited atom is electrically neutral. [1]
Atoms are electrically neutral particles with equal numbers of electrons and protons. In this case, the
atom has 11 electrons (2 + 7 + 2) and 11 protons. [1 point]
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24. Base your answer on the information below.
An atom in an excited state has an electron configuration of 2-7-2.
Write the electron configuration of this atom in the ground state. [1]
Use the Periodic Table of the Elements. The ground-state electron configuration of Na (atomic
number 11) is 2-8-1. [1 point]
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25. Explain, in terms of protons and neutrons, why U-235 and U-238 are different isotopes of
uranium. [1]
Isotopes of an element have the same atomic number but different mass numbers. This means that
each isotope has the same number of protons but a different number of neutrons. A U-235 atom has
92 protons and 143 neutrons, and a U-238 atom has 92 protons and 146 neutrons.
[1 point]
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26. Base your answer on the accompanying information.
The accompanying bright-line spectra for three elements and a mixture of elements are shown.
Explain, in terms of both electrons and energy, how the bright-line spectrum of an element is
produced. [1]
As excited electrons fall back to lower energy levels, energy is emitted in the form of light.
[1 point]
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27. Base your answer on the accompanying information.
The accompanying bright-line spectra for three elements and a mixture of elements are shown.
Identify all the elements in the mixture. [1]
The bright-line spectrum of a mixture of elements will contain all of the lines of each element in the
mixture. Compare the spectra of each element with the spectrum of the mixture. The mixture
contains strontium and lithium.
[1 point]
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28. Base your answer on the accompanying information.
The accompanying bright-line spectra for three elements and a mixture of elements are shown.
State the total number of valence electrons in a cadmium atom in the ground state. [1]
Valence electrons are those in the outermost shell of an atom. Use the Periodic Table of the
Elements. Cadmium (Cd, element 48) has the ground-state electron configuration 2-8-18-18-2.
Therefore, cadmium has two (2) valence electrons.
[1 point]
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29. One electron is removed from both an Na atom and a K atom, producing two ions. Using
principles of atomic structure, explain why the Na ion is much smaller than the K ion. Discuss both
ions in your answer. [2]
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30. Base your answer on the diagram (see image), which shows bright-line spectra of selected
elements.
On a separate sheet of paper identify the two elements in the unknown spectrum. [2]
Compare the positions of the lines in the unknown sample with the positions of the lines in the
elements given above it. The unknown sample is a mixture of hydrogen (H) and helium (He).
Note: One point is awarded for identifying each of the elements present. [2 points]
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31. Base your answer on the diagram (see image), which shows bright-line spectra of selected
elements.
Explain how a bright-line spectrum is produced, in terms of excited state, energy transitions, and
ground state. [2]
In order to produce a bright-line spectrum, energy must be absorbed by atoms, raising the electrons
from the ground state to one or more excited states. As the electrons return to lower energy levels
(shells), the energy that is released forms the bright-line spectrum.
Note: One point is awarded for explaining the change from the excited state to the ground state, one
point is awarded for explaining the release of energy. [2 points]
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32. Base your answers to the question on the information below.
Two isotopes of potassium are K-37 and K-42.
How many valence electrons are in an atom of K-42 in the ground state?
The valence electrons are those electrons that occupy the outermost level of the atom. Use the
Periodic Table of the Elements. The electron configuration of potassium (K) is 2-8-8-1; an atom of
potassium has 1 valence electron. [1 point]
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33. In the space provided or on a separate sheet of paper, draw a Lewis electron-dot diagram for a
sulfur atom in the ground state. [1]
Refer to the Periodic Table of the Elements. The ground-state electron configuration of sulfur (S) is
2-8-6. An atom of sulfur contains 6 valence electrons, which appear in the Lewis diagram. Two
acceptable diagrams are shown: [1 point]
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34. Write an electron configuration for an atom of aluminum-27 in an excited state. [1]
Refer to the Periodic Table of the Elements. The ground-state electron configuration of any isotope
of aluminum (Al) is 2-8-3. An excited atom is one in which one or more electrons have been
promoted to higher shells. Remember: The first shell may contain no more than 2 electrons, and the
second shell may contain no more than 8. Some acceptable examples are:
2-7-4 1-8-4 2-6-2-3
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35. Base your answer on the information below.
The accepted values for the atomic mass and percent natural abundance of each naturally occurring
isotope of silicon are given in the accompanying data table.
Determine the total number of neutrons in an atom of Si-29. [1]
Refer to the Periodic Table of the Elements. The atomic number of an atom of silicon (Si) is 14 and
is equal to the number of protons in the nucleus of the atom. The mass number of the isotope Si-29
is 29 and is equal to the sum of the number of protons and neutrons in its nucleus. Therefore the
number of neutrons is equal to 29 – 14 = 15.
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36. Base your answer on the information below.
The accepted values for the atomic mass and percent natural abundance of each naturally occurring
isotope of silicon are given in the accompanying data table.
In the space provided, or, if taken online, on a separate piece of paper, show a correct numerical
setup for calculating the atomic mass of Si. [1]
To calculate the (average) atomic mass of the element Si, multiply the atomic mass of each isotope
by the decimal equivalent of the percent natural abundance, as shown below:
(average) atomic mass = (27.98) · (0.922)+(28.98) · (0.0469)+(29.97) · (0.0309)
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37. Base your answer on the information below.
Elements with atomic numbers 112 and 114 have been produced and their IUPAC names are
pending approval. However, an element that would be put between these two elements on the
Periodic Table has not yet been produced. If produced, this element will be identified by the symbol
Uut until an IUPAC name is approved.
Determine the charge of an Uut nucleus. Your response must include both the numerical value and
the sign of the charge. [1]
The atomic number of Uut is 113. Therefore, the nuclear charge is +113.
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38. Base your answer on the information in the accompanying table.
State, in terms of subatomic particles, how an atom of Cu-63 differs from an atom of Cu-65. [1]
Refer to the Periodic Table of the Elements. Since both atoms are copper (Cu), both have 29 protons
in their nuclei. The mass number of an atom is the sum of the protons and neutrons in its nucleus.

An atom of Cu-63 has 63 – 29 or 34 neutrons in its nucleus.

An atom of Cu-65 has 65 – 29 or 36 neutrons in its nucleus.
Therefore, an atom of Cu-63 has fewer neutrons than an atom of Cu-65. [1 point]
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39. Base your answer on the information in the accompanying table.
What is the total number of electrons in an atom of Cu-65? [1]
An atom is a neutral particle. The number of protons must be equal to the number of electrons. Since
copper contains 29 protons, it also contains 29 electrons. [1 point]
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40. Base your answer on the information in the accompanying table.
In the space on the answer sheet or on a separate piece of paper, show a correct numerical setup for
calculating the atomic mass of copper. [1]
To calculate the (average) atomic mass of the element Cu, multiply the atomic mass of each isotope
by the decimal equivalent of the percent natural abundance, as shown below:
(average) atomic mass = (62.930) · (0.6917) + (64.928) · (0.3083) [1 point]
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41. Base your answer on the information below.
In a laboratory, a glass tube is filled with hydrogen gas at a very low pressure. When a scientist
applies high voltage between metal electrodes in the tube, light is emitted. The scientist analyzes the
light with a spectroscope and observes four distinct spectral lines. The accompanying table gives the
color, frequency, and energy for each of the four spectral lines. The unit for frequency is hertz, Hz.
Explain, in terms of subatomic particles and energy states, why light is emitted by the hydrogen gas.
[1]
Light is emitted when a hydrogen atom changes from a higher to a lower energy state. This change
corresponds to an electron dropping from a higher electron shell to a lower one. [1 point]
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42. Describe the electrons in an atom of carbon in the ground state. Your response must include:

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
the charge of an electron [1]
the location of electrons based on the wave-mechanical model [1]
the total number of electrons in a carbon atom [1]

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An electron has a negative charge.
According to the wave-mechanical model, electrons are located in orbitals (or regions of
most probable location).
An atom of carbon has a total of 6 electrons.

One point is awarded for each acceptable response. [3 points]
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43. On a separate piece of paper, write an electron configuration for a silicon atom in an excited
state. [1]
Refer to the Periodic Table of the Elements. The ground-state electron configuration for an atom of
silicon (Si, atomic number 14) is 2–8–4. An excited atom has one or more of its electrons promoted
to a higher energy level. Many different configurations are possible, including 2-7-5, 1-8-5, and 2-83-1.
Note that only one configuration needs to be given in order to receive credit. [1 point]
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44. Base your answer on the information below.
In the gold foil experiment, a thin sheet of gold was bombarded with alpha particles. Almost all the
alpha particles passed straight through the foil. Only a few alpha particles were deflected from their
original paths.
State one conclusion about atomic structure based on the observation that almost all alpha particles
passed straight through the foil. [1]
Since most of the alpha particles passed through without deflection, Rutherford concluded that
atoms consist mostly of empty space. [1 point]
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45. Base your answer on the information below.
In the gold foil experiment, a thin sheet of gold was bombarded with alpha particles. Almost all the
alpha particles passed straight through the foil. Only a few alpha particles were deflected from their
original paths.
Explain, in terms of charged particles, why some of the alpha particles were deflected. [1]
Alpha particles are positive, and a few were repelled by the positively charged nucleus. [1 point]
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46. In the early 1900s, evidence was discovered that atoms were not "hard spheres." It was shown
that atoms themselves had an internal structure. One experiment involved gold metal foil.
a On the diagram shown or one similar, complete the simple model for an atom of gold-197 by
placing the correct numbers in the two blanks. [1]
b In the gold-foil experiment, alpha particles were directed toward the foil. Most of the alpha
particles passed directly through the foil with no effect. This result did not agree with the "hard
spheres model" for the atom. What conclusion about the internal structure of the atom did this
evidence show? [1]
c In the same experiment, some of the alpha particles returned toward the source. What does this
evidence indicate about the charge of the atom's nucleus? [1]