ATOMIC STRUCTURE UNIT REVIEW SHEET
NAME: __________________________
SHORT ANSWER Answer the following questions in the space provided.
1. Why is Democritus’s view of matter considered only an idea, while Dalton’s view is considered a
theory?
_______________________________________________________________
2. Give an example of a chemical or physical process that illustrates the law of conservation of mass.
_______________________________________________________________
3. State two principles from Dalton’s atomic theory that have been revised as new information has become
available.
_______________________________________________________________
_______________________________________________________________
4. The formation of water according to the equation
2H2 + O2  2H2O
shows that 2 molecules (made of 4 atoms) of hydrogen and 1 molecule (made of 2 atoms) of oxygen
produce 2 molecules of water. The total mass of the product, water, is equal to the sum of the masses of
each of the reactants, hydrogen and oxygen. What parts of Dalton’s atomic theory are illustrated by this
reaction? What law does this reaction illustrate?
_______________________________________________________________
_______________________________________________________________
Write the answer on the line. Show all your work in the space provided.
5.Nitrogen and oxygen combine to form several compounds, as shown by the following table.
Compound Mass of nitrogen that combines with 1 g oxygen (g)
NO
NO2
NO4
1.70
0.85
0.44
Calculate the ratio of the masses of nitrogen in each of the following:
_____ a.
NO
NO 2
_____ b.
NO 2
NO 4
______ c.
NO
NO 4
Which law do these data illustrate? _The Law of ___________________________________________
MIXED REVIEW
SHORT ANSWER Answer the following questions in the space provided.
6. The element boron, B, has an atomic mass of 10.81 amu according to the periodic table. However, no
single atom of boron has a mass of exactly 10.81 amu. How can you explain this difference?
_______________________________________________________________
_______________________________________________________________
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7. How did the outcome of Rutherford’s gold-foil experiment indicate the existence of a nucleus?
_______________________________________________________________
_______________________________________________________________
8. Complete the following table about ATOMS of each:
Atomic Mass
Number of
Element
Symbol number number protons
Na
11
11
Fluorine 9
𝟖𝟎
Bromine - 80
35
35
𝟑𝟓𝑩𝒓
Ca
20
Hydrogen - 1
H
1
1
Radon 86
86
Number of
neutrons
11
10
20
Number of
electrons
11
9
35
20
1
136
PROBLEMS Write the answer on the line to the left. Show all your work in the space provided.
9. __________________ a. How many atoms are there in 2.50 mol of copper?
__________________ b. How many grams are there in 2.50 mol of uranium?
__________________ c. How many moles are present in 107 g of sodium?
10. A certain element exists as three natural isotopes, as shown in the table below.
Isotope
Mass (amu)
Percent natural
abundance
Mass number
1
2
3
19.99244
20.99395
21.99138
90.51
0.27
9.22
20
21
22
__________________ Calculate the average atomic mass of this element. SHOW WORK BELOW!
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In the space provided, write the letter of the correct term or phrase that best best answers each question.
_____ 11. John Dalton thought that atoms
a. contain molecules.
b. cannot be broken down further.
c. are all composed of carbon.
d. have no mass.
_____ 12. Using improved chemistry equipment in the late 1700s, chemists observed that mass is neither
created nor destroyed in a chemical reaction. This scientific law is called the law of
a. definite proportions.
b. gravity.
c. conservation of mass.
d. conservation of momentum.
_____ 13. The fact that every sample of a particular chemical compound contains the same elements in
exactly the same proportions by mass is known as the law of
a. conservation of energy.
b. conservation of mass.
c. atomic theory.
d. definite proportions.
_____ 14. If two or more compounds are composed of the same two elements, then the ratio of the masses
of the second element that is combined with a certain mass of the first element is always a ratio
of small whole numbers. This statement is called the law of
a. definite proportions.
b. conservation of mass.
c. atomic theory.
d. multiple proportions.
_____ 15. In 1808, John Dalton established his atomic theory. Which of the following is not part of
Dalton’s atomic theory?
a. All matter is composed of atoms.
b. An atom consists of a nucleus and a cloud of electrons.
c. Atoms cannot be subdivided, created, or destroyed.
d. In chemical reactions, atoms are combined, separated, or rearranged.
_____ 16. Which of the following statements of Dalton’s atomic theory describes conservation of mass?
a. All matter is composed of atoms.
b. Atoms of a given element are identical in size, mass, and other properties.
c. Atoms cannot be subdivided, created, or destroyed.
d. Atoms of different chemical elements combine in simple whole-number ratios to form
chemical compounds.
_____ 17. Which of the following statements of Dalton’s atomic theory describes the law of multiple
proportions?
a. All matter is composed of atoms.
b. Atoms of a given element are identical in size, mass, and other properties.
c. Atoms cannot be subdivided, created, or destroyed.
d. Atoms of different chemical elements combine in simple whole-number ratios to form
chemical compounds.
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_____ 18. Which is one way that Dalton’s atomic theory has been shown to be incorrect?
a. Atoms can change identity in chemical reactions.
b. Atoms can be split into subatomic particles.
c. Atoms can be destroyed by chemical reactions.
d. Some atoms of a particular element are identical to atoms of other elements.
SHORT ANSWER Answer the following questions in the space provided.
19. In cathode-ray tubes, the cathode ray is emitted from the negative electrode, which is called the
________________.
20. The smallest unit of an element that can exist either alone or in molecules containing the same or
different elements is the ________________.
21. A positively charged particle found in the nucleus is called a(n) ________________.
22. A nuclear particle that has no electrical charge is called a(n) ________________.
23. The subatomic particles that are least massive and most massive, respectively, are the
________________ and ________________.
24. A cathode ray produced in a gas-filled tube is deflected by a magnetic field. A wire carrying an electric
current can be pulled by a magnetic field. A cathode ray is deflected away from a negatively charged
object. What property of the cathode ray is shown by these phenomena?
_______________________________________________________________
25.Is an atom positively charged, negatively charged, or neutral?
_______________________________________________________________
26. Below are illustrations of two scientists’ conceptions of the atom. Label the electrons in both
illustrations with a  sign and the nucleus in the illustration to the right with a + sign. On the lines
below the figures, identify which illustration was believed to be correct before Rutherford’s gold-foil
experiment and which was believed to be correct after Rutherford’s gold-foil experiment
.
a. __________________________
b. ___________________________
27. In the space provided, describe the locations of the subatomic particles in the
labeled model of an atom of nitrogen below, and give the charge and relative
mass of each particle.
a. proton ___________________________________________________
b. neutron___________________________________________________
c.electron (a possible location of this particle)
_______________________________________________________________
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In the space provided, write the letter of the correct term or phrase that best completes each statement or
best answers each question.
_____ 28. Experiments with cathode rays being deflected by a magnetic field show that cathode rays are
composed of particles that are
a. magnetic.
b. negatively charged.
c. positively charged.
d. neutral in charge.
_____ 29. Cathode rays are composed of particles that are now known as
a. positrons.
b. neutrons.
c. protons.
d. electrons.
_____ 30. In 1911, Ernest Rutherford conducted his now famous goldfoil experiment. During the
experiment, alpha particles bombarded a thin piece of gold foil. The alpha particles were
expected to pass easily through the gold foil. Every now and then, however, an alpha particle
bounced back—an unexpected result. Rutherford concluded that these particles were striking
a. a tiny region of positive charge.
b. a dense region of negative charge.
c. a dense region of neutrons.
d. a tiny region with a strong magnetic field.
_____ 31. Rutherford called the region that deflected alpha particles
a. an electron.
b. a positron.
c. a nucleus.
d. a quark.
_____ 32. The total volume of the nucleus of an atom is
a. very large compared with the rest of the atom.
b. very small compared with the rest of the atom.
c. about the same size as an electron.
d. smaller than a neutron.
_____ 33. Except for in the simplest type of hydrogen atom, all nuclei consist of
a. protons and electrons.
b. neutrons and positrons.
c. protons and neutrons.
d. electrons and positrons.
_____ 34. Electrons can be found
a. inside protons.
b. inside neutrons.
c. attached to the nucleus.
d. moving rapidly outside the nucleus.
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_____ 35. We know that objects with like electric charge repel one another. Which statement best explains
why protons can remain close to one another in a nucleus?
a. There is no electric charge in the nucleus of an atom.
b. A short-range force, called the strong nuclear force, binds protons together.
c. Protons are balanced electrically by electrons.
d. Neutrons cancel out the electric force.
_____ 36. Most of an atom is
a. dense.
b. fluid.
c. empty.
d. the nucleus.
_____ 37. What is the charge of a neutron?
a. positive
b. negative
c. neutral
d. None of the above
SHORT ANSWER Answer the following questions in the space provided.
38. Explain the difference between the mass number and the atomic number of a nuclide.
_______________________________________________________________
_______________________________________________________________
39. How many particles are in 1 mol of carbon? 1 mol of lithium? 1 mol of eggs? Will 1 mol of each of
these substances have the same mass?
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
40. List the number of protons, neutrons, and electrons found in zinc-66.
______ Protons _______ neutrons _________electrons
PROBLEMS Write the answer on the line to the left. Show all your work in the space provided.
41. _________________
What is the mass in grams of 2.000 mol of oxygen atoms?
42. _________________
How many moles of aluminum exist in 100.0 g of aluminum?
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43. _________________
How many atoms are in 80.45 g of magnesium?
In the space provided, write the letter of the correct term or phrase that best completes each statement or
best answers each question.
_____ 44. The atomic number of an element is
a. the mass of the element.
b. 1 mol of the element.
c. the number of protons in each atom of the element.
d. the number of neutrons in each atom of the element.
_____ 45. Hydrogen that is composed of atoms with two neutrons is called
a. protium.
b. deuterium.
c. tritium.
d. helium.
_____ 46. Isotopes are atoms of the same element that have different
a. masses.
b. charges.
c. numbers of electrons.
d. atomic numbers.
_____ 47. Mass number is
a. the average atomic mass of an element.
b. the total number of electrons in an atom of an element.
c. the total number of protons in an atom of an element.
d. the total number of protons and neutrons in an atom of an element.
_____ 48. The isotope uranium-235 has 92 protons and 143 neutrons. Therefore, its mass number is
a. 92.
b. 235.
c. 143.
d. impossible to determine.
_____ 49. The nuclear symbol for uranium-235 should be written as
a. U-235.
b. 235
c. 235
d. U.
92 U.
143 U.
_____ 50. What is the definition of one atomic mass unit?
a. 1 g of any element
b. 1 mol of any element
1
c.
of the mass of a carbon-12 atom
12
1
d.
of the mass of any atom
12
_____ 51. To take a weighted average of all the naturally occurring isotopes of an element in order to
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arrive at an average atomic mass, you would
a. multiply the mass of each isotope by the decimal fraction representing its abundance
naturally, then add all these products together.
b. use the isotope with the largest mass.
c. use the isotope with the most average mass.
d. add all the masses of all of the isotopes, then divide by the number of isotopes.
_____ 52. One mole is defined as
a. the volume of a substance with a mass of 12 g.
b. the amount of a substance that contains as many particles as there are atoms in exactly 12 g
of carbon-12.
c. the amount of a substance that contains as many particles as there are atoms in exactly 12 g
of silver.
d. an amount of a substance that contains enough atoms to have a mass of 12 g.
_____ 53. According to the Bohr model of the atom, which particles are allowed to exist in any one of a
number of energy levels?
a. electrons
b. protons
c. neutrons
d. Both (b) and (c)
_____ 54. Because excited hydrogen atoms always produced the same line-emission spectrum, Bohr
concluded that hydrogen
a. has no electrons.
b. does not release energy.
c. releases energy of only certain values.
d. can exist only in the ground state.
55. _____ According to Bohr, which is the point in the figure below where electrons cannot reside?
(a) point A
(c) point C
(b) point B
(d) point D
_____ 56. Which mathematically describes the wave properties of electrons?
a. quantum theory
b. atomic theory
c. the Bohr model of the atom
d. the Rutherford model of the atom
57. Define ION. __________________________________________________________________
58. A positive ion is called a _____________________ and is formed by an atom ______________
electrons.
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59. A negative ion is called a ____________________ and is formed by an atom _______________
electrons.
60. True or false: the number of protons in an atom identifies the element. ___________________
61. Complete the following table. SOME are ions so be careful!
Atomic Mass
Number of Number of Number of
Symbol number number protons
neutrons
electrons
22
1+
𝑵𝒂
11
11
𝟏−
𝑭
9
10
34
80
36
40
2+
𝐶𝒂
20
H
1
1
211 5+
𝐵𝑖
62. Describe the atom as it would have appeared to each of these scientists. You can DRAW and label
if you would rather! If the model shown/described has a name, include it! HINT: these are listed in
chronological progression – memorize them in ORDER and look for how the atomic model
progressed!
Democritus:
Dalton:
Thomson:
Rutherford:
Bohr:
Chadwick:
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63. Describe the major contribution of each scientist to ATOMIC THEORY, include a few details about
the experiments that led to the contributions.
Dalton: (list the ideas of his atomic theory!)
Thomson:
Millikan:
Rutherford:
Bohr:
Chadwick:
DeBroglie:
Heisenberg:
Planck:
Curie:
Lavoisier:
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