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Atomic Structure and Nuclear Chemistry Test: Unit 3
Chemistry, Mr. Williamson
Name: _____________________
Date: March 12, 2010
I. Matching Terms: (2 points each)
Use the definitions from the end of this test to match with these terms
___ isotope
____ cation
____ alpha particle
____ beta particle
____ anion
___ proton
____ Half Life
___ atom
____ electron
(____ / 20)
____ neutron
II. Multiple Choice Answers: (1.5 points each)
Record your answers for the Multiple Choice questions at the end of this test:
1) ____
2) ____
3) _____
4) _____
5) _____
6) _____
7) _____
8) _____
9) _____
10) ____
11) ____
12) ____
13) _____
14) ____
15) ____
16) ____
18) _____
19) _____
20) _____
21) ____
22) ____
Complete this table. (0.3 pts each box)
Name
Symbol
(___ / 33)
17) ___
(___ / 10 pts)
Atomic
Mass
Number Number
#
protons
#
electrons
#
charge
neutrons
25
12
Mg+2
14
Fluorine-18
Alpha particle
any one you want
9
29
14
15
9
-1
Name: ______________________
III. Atomic Theory Work: Answer each of the following questions (6 pts each)
1) There is a metal element that has three naturally occurring isotopes. Their masses
are 58 amu, 59 amu and 60 amu.
a. Calculate the average atomic mass of this element given the following data:
Show your work
Mass number Percent Abundance
58
55.07 %
59
25.68%
60
19.35 %
b. Identify the element from your periodic table: _____________________
c. Explain why the relative abundance of each isotope is used to find the
average atomic mass, and not a total number of atoms in a sample.
2) JJ Thomson divided the atom into at least two parts. One part was seen as a beam
leaving the cathode in a cathode ray tube. It is drawn below.
a. What particle did Thomson separate from the atom? ________________
b. What charge is on that particle? _________________
c. Draw the path these particles take when the magnet below is brought near
the Crookes’ Tube.
cathode
anode
-
Power Supply
+
magnet
d. Draw some representation that is clearly labeled of what JJ Thomson
thought the atom looked like due to his study of the atom.
3) Ernest Rutherford used gold foil and alpha particles to study the structure of the
atom. Using the observations below, draw two logical conclusions about the
structure of the atom.
a. Observation: Rutherford saw that the majority of the alpha particles that
he fired toward a thin gold foil were not affected in any way by the foil.
Conclusion:
b. Observation: Rutherford saw that a small percentage (0.038%) of alpha
particles would bounce off the gold foil as if they hit a solid wall.
Conclusion:
c. Explain the major shift between Thomson’s plum pudding model of the
atom and Rutherford’s model of the atom. Include at least two drawings
as part of your answer.
4) Ernest Rutherford was able to learn about the atom’s structure with gold foil and
alpha particles. Today, we have far exceeded his ability to “look” at the atom.
Current studies have been able to measure the radius of atoms. Other studies have
been able to determine the radius of the nucleus of atoms. Use the data below to
confirm or refute Rutherford’s conclusion about the atom.
The radius of a sodium atom is 1.86 x 10-12m.
Volume of a sphere is Vsphere = 4/3 r3
The radius of a sodium nucleus is 3.04 x 10-15m.
The mass of a sodium ATOM is 3.82 x 10-23 g.
The mass of a sodium NUCLEUS is (for all intensive purposes) the same.
a. What is the density of the nucleus of sodium?
b. What is the density of an atom of sodium?
c. Explain how these calculations support or refute Rutherford’s findings.
Be sure to mention Rutherford’s findings in your explanation.
IV. Nuclear Chemistry:
Answer these questions
( ___ / 13)
1) Finish the following these nuclear reactions. (3 pts each)
a.
26
13
Al 
12
6
C + ____
b.
39
19
2
K + 1H
37
18
Ar + ____
2) Rutherford used isotopes of polonium in his gold foil experiment as a source of
alpha particles. Each atom of polonium-210 produces 2 alpha particles and a
neutron. What isotope is formed when one atom of polonium-210 gives off 2
alpha particles and one neutron? Write the reaction of this nuclear decay. (3 pts)
a.
210
84
Po 
3) When an unstable isotope undergoes a beta decay one of the neutrons in the
nucleus breaks into two parts. One part is emitted from the nucleus as the beta
particle. The other part remains in the nucleus.
a. Describe the two pieces in more detail (2 pts)
b. Complete the reaction below so that it that shows neptunium-237
undergoing beta decay. (2 pts)
237
93
Np 
Matching Definitions
A. An electron that is emitted from an unstable nucleus because a neutron decayed into a
proton and an electron.
B. One of the two sub-atomic particles that has a mass of 1 amu. It has no electrical
charge.
C. One of the two sub-atomic particles that has a mass of 1 amu. It has a positive electrical
charge.
D. The third sub-atomic particle. Its mass is nearly 2000 time smaller than the other
two. It carries a negative electrical charge.
E. an individual atom of an element with a different number of neutrons in the nucleus than
another atom of the same element
F. A stable, neutral collection of protons, neutrons and electrons that are identifiable
as an element.
G. The amount of time it takes half the mass of a sample of radioactive matter to decay.
H. Any particle that has more electrons than protons
I. Any particle that has fewer electrons than protons
J. Two protons and two neutrons that are emitted at once from an unstable nucleus
Multiple Choice Questions
Select the best answer to these questions in the blanks on the first page of the test.
Record your answer neatly and clearly. There is only one best answer for each question.
1) This term is defined by the number of protons in an atom.
a. Atomic Mass
c. Atomic Weight
b. Average Atomic Weight
d. Atomic Number
2) This term is the sum of the protons and neutrons in an atom’s nucleus.
a. Atomic mass number
c. Average atomic weight
b. Atomic number
d. Nuclear Mass
3) What is the approximate mass of one electron?
a. 1 amu
b. 1/2000th amu
c. -1 amu
d. 1 gram
4) Which chemical species contains the greatest number of electrons?
(A)
58
3+
26Fe
(B)
56
0
26Fe
(C)
58
2+
26Fe
(D)
56
3+
26Fe
5) Which of the following is NOT a portion of Dalton’s Atomic Theory?
a. The nucleus of the atom is small dense and positive
b. Atoms exist as indivisible indestructible particles.
c. The ratio of each element in a compound is the same for the same
compounds and is different for different compounds.
d. elements form compounds in whole number ratios
6) You find the mass of an atom and compare your value to the one on the
Periodic Table. The value presented on the Periodic Table is different than
the one you determined. Why?
a. The Periodic Table shows values that are weighted averages of the
isotopes, while you found the actual mass of one atom.
b. Rounding and estimations limit accuracy in your measurements.
c. Your value is in grams while the Periodic Table presents values in amu
d. The Periodic Table gives values rounded for easier use.
7) What is the difference between an atom of lead-207 and an atom of lead-208?
a. Nothing
b. Lead-207 has one less proton than lead-208
c. Lead-207 has one less neutron than lead-208
d. Lead-207 has one less electron than lead-208
e. B and D are both correct
8) If atom A contains 18 protons and 22 neutrons, while atom B contains 20
protons and 20 neutrons, then atoms A and B are
a. isotopes.
d. both very reactive
b. both non–reactive (inert).
e. alike in number of electrons.
c. different in number of electrons.
9) According to Democritus’s ideas about “atomos” which one of the following
is TRUE?
a. Atomos are divisible.
b. Atomos are hard dense spheres
c. Atomos have varying density – they are heterogeneous.
d. Changes in matter are due to the changes in atomos.
10) Which of the following statements was not part of Dalton’s atomic theory?
a. All matter is made of small particles called atoms.
b. Atoms are divisible.
c. Atoms of different elements have different chemical and physical properties.
d. Atoms can be separated from each other, combined with each other or
rearranged when reacting.
11) The number of neutrons in an atom of an element is
a. the same in each isotope.
b. the same as the atomic number.
c. equal to the number of electrons.
d. equal to the number of protons in the nucleus.
e. equal to the difference between the mass number and the atomic number.
2
12) The difference between deuterium, (1H)) and the more common form of
hydrogen (11H) is that deuterium…
a. does not occur in nature.
b. is naturally radioactive.
c. has one more atom per molecule.
d. has one more proton in the nucleus.
e. has one neutron in the nucleus.
13) A proton is approximately this many times more massive than an electron.
a. 20
b. 200
c. 2,000
d. 2,000,000
14) A cation is formed when …
a. An electron is taken away from a neutral atom
b. An electron is added to a neutral atom
c. An alpha particle passes through a nucleus
d. A proton leaves a stable nucleus
15) Where in the atom are the electrons most often found?
a. in the nucleus
b. as part of neutrons
c. outside the nucleus
16) This scientist determined that atoms combine in whole number ratios to form
new substances.
a. Democritus
c. Rutherford
b. Thomson
d. Dalton
17) This type of radiation is best described as pure energy.
a. Alpha
b. Beta
c. Gamma
d. Neutron
18) If a particle has a half life of 12 days, how many days will it take for a 50
gram sample to decay into a 6.25 gram sample?
a. 12 days
b. 18 days
c. 24 days
d. 30 days
e. 36 days
19) Why do all nuclear reactions need to be balanced?
a. Dalton’s Law of Definite Proportions
b. Democritus’s atomos philosophy
c. The Law of conservation of mass
d. Rutherford’s conclusion that atoms have a small dense positive nucleus.
20) What is the approximate mass of an electron in grams?
a. 1 x 1029g
b. 1 x 10-200 g
c. 1 x 10-28g
d. 1 x 10-3 g
21) Which subatomic particles identify an atom as a specific element?
a. Electrons and neutrons
b. Electrons and protons
c. Only the Neutrons needs to be known
d. All three need to be known to identify which element an atom is
22) What type of particle is created when an electron is added to a neutral atom?
a. An isotope
b. An alpha particle
c. A cation
d. An anion