PA
Problem Set 2a
The Structure of the Atom and Nuclear Chemistry
Chapters 4 and 25
Due Wednesday March 16th
Test Friday March 18th
 Your work is to be done on separate sheets of paper.
 All of the papers should be stapled together in the upper left hand corner with this
question sheet at the back of the packet.
 Each of your responses should be numbered the same way as it appears on this packet.
You should read chapters 4 and 25 as we progress through this unit.
Chapter 4 The Structure of the Atom
Chapter 25 Nuclear Chemistry
4-1 Early Theories of Matter
4-2 Subatomic Particles
4-3 How Atoms Differ
4-4 Radioactive Decay
25-1 Nuclear Radiation
25-2 Radioactive Decay
25-3 Transmutation
25-4 Fission and Fusion
25-5 Science and Radiation
Section 4-1Early Theories of Matter
Conceptual questions
1) What are the 5 components of Democritus’s Atomic Philosophy?
2) What is wrong with Democritus’s ideas?
3) What are the 5 components of Dalton’s Atomic Theory?
4) What is wrong with Dalton’s Atomic Theory?
Practice Questions
5) True False Questions – determine if the following statements are true or false
according to Democritus’s ideas about atomos.
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.
6) True False Questions – determine if the following statements are true or false
according Dalton’s Atomic Theory
a. All matter is made of small particles called atoms.
b. Atoms are divisible.
c. Atoms of the same element are identical
d. Atoms can be separated, combined or rearranged
Extension Questions
7) What is a Scanning Tunneling Microscope? Briefly describe what it does and
why it is an important tool for scientists.
8) Why is Dalton’s Atomic theory still taught in school, even though it is over 200
years old?
Section 4-2: Sub-Atomic Particles and the Nuclear Atom
Conceptual Questions
9) The cathode ray tube was used to discover the electron. Re-Draw the diagram
from your notes (or page 92) and include what the ray looks like when the
positive end of a magnet is brought near the ray.
10) What key conclusions did Thomson draw from his observations?
11) Rutherford used radioactive material to fire positively charged particles at thin
sheets of metal.
a. What is the name of those particles?
b. What is the composition of those particles?
12) Create a diagram of Rutherford’s Gold Foil Experiment. Be sure to include the
following details: the alpha particles, radioactive polonium, zinc sulfide lining,
gold foil, and the location of the most hits, some hits, and only a few hits.
13) What were Rutherford’s two observations from his famous experiment?
14) What were the two conclusions that correspond to the Rutherford’s two
observations? Be sure to connect each conclusion with the appropriate
observation.
Practice Questions
15) Who determined that electrons exist?
16) Who determined the mass of an electron?
17) What is the mass of an electron?
18) Who determined that the nucleus of an atom exists?
19) Who determined the charge of nucleus?
20) What is the charge of the nucleus?
21) Who determined that neutrons exist?
22) What is the mass of a proton?
23) What is the mass of a neutron?
Extension Questions
24) Draw three historical pictures of an atom if we could take a picture of it…be as
detailed as possible
a. Dalton’s Perspective
b. Thomson and Millikan’s Perspective
c. Rutherford and Chadwick’s Perspective
25) Propose a reason for a neutron to be ever so slightly more massive than a proton.
Section 4-3 How Atoms Differ
Conceptual Questions
26) Define the following terms
a. Atomic number
b. Isotope
c. Average Atomic Mass
d. Percent Abundance
27) How are isotopes of the same element alike?
28) How are isotopes of the same element different?
29) What sub-atomic particle(s) identify/(ies) an element?
30) What sub-atomic particle(s) determine(s) the isotope of an element?
31) Use the data below to calculate the average atomic weight for compound X. Then
use your periodic table to identify element X.
Isotope 1 = 90. 00 %, 39 a.m.u.
Isotope 2 = 9.000 %, 40 a.m.u.
Isotope 3 = 1.000 %, 41 a.m.u.
32) One of the stable isotopes of tins is tin-119. The atomic number of tin is 50. How
many protons, neutrons and electrons are in one atom of this isotope of tin?
33) What is the atomic mass of an isotope of potassium that has 21 neutrons?
Practice Questions
34) Fill in this table for each atom or ion. You may write on the Problem Set… rather
than re-draw the table in your responses.
Isotope
Symbol
# p+ #e - #no
Atomic
Mass
Charge
Name
Number
Number
118
Tin - 118
68
0
50
Sn
19
19
18
F -1
40
10
-1
7
-3
9
10
52
128
tellurium - 128
Extension Questions
35) List the steps needed to calculate the average atomic mass if you are given the
relative abundance and mass of each isotope known to exist.
36) Nitrogen has two naturally occurring isotopes: nitrogen-14 and nitrogen-15. The
average atomic mass of nitrogen is 14.0007 amu. Which isotope is more
abundant? Explain.
Section 4-4: Radioactive Decay
Conceptual Questions
37) State the law of conservation of mass.
38) Why are atoms unstable?
39) How do unstable atoms gain stability?
40) A radioactive element having atomic number 82 and atomic mass 214 loses a beta
0
particle, –1. What is the resulting particle?
41) What type of decay is the reaction below, and what isotope completes this nuclear
equation?
27
2
4
13Al + 1H  2He + ?
Practice Questions
42) Complete this chart on the three types of radioactive decay
Type
Symbol
Mass (amu)
Alpha
Beta
Gamma
Charge
238
43) If the radioactive atom 92U emits an alpha particle, the atom remaining is
represented by
(A)
238
92U
(B)
236
92Th
(C)
234
92U
(D)
32
30
234
234
90Th
(E) 91Pa
0
44) What term completes this equation? 14Si + ?  16S + –1e
4
(A)2He
2
1
(B)1H
0
(C)1H
(D) –1e
214
45) What particle is emitted when lead–214, 82Pb, undergoes natural radioactive
214
decay to bismuth–214, 83Bi?
4
(A)
an alpha particle, 2He
(B)
a beta particle, –1e
0
1
(C)
a proton, 1H
(D)
a neutron, 0n
1
Extension Question
46) Recently Alexander Valterovich Litvinenko was poisoned by radioactive
polonium-210.
a. Research who he was and why he was poisoned.
b. Find out what polonium-210 does to people.
c. Write the nuclear reaction of polonium-210 decaying into lead-206 via an
alpha decay.
Chapter 25 Nuclear Chemistry Read Chapter 25
After having read through chapter 25, respond to these conceptual questions.
47) Define the following terms:
a. critical mass
d.fusion
g.radioisotope
b.decay
e. half life
c. fission
f. transmutation
48) Make (or find) a graphical timeline of the development of modern atomic theory
with at least 10 important dates and/or discoveries.
After having read through chapter 25, respond to these practice questions.
49) Which type of radiation has a +2 charge?
a. Alpha
b. beta
c. gamma
d. neutron
50) Which type of radiation generates the highest energy – is the “hardest” to block?
a. Alpha
b. beta
c. gamma
d. neutron
51) Finish the following nuclear reactions. Tell if they are alpha or beta decays.
a.
b.
238
234
92
90
19
9
U
Th + ____
19
F  ___+ 10 Ne
c. 222
86
d.
4
Rn  ___ + 2He
210
85
0
At  ___ +-1
52) What element was the first synthesized by scientists (namely) Ernest Rutherford?
53) How many grams of sample are left after 20 minutes if 100 grams start decaying
with a half life of 5 minutes?
54) How long will it take 100 grams of radioactive sample to decay so that only 6.25
grams remain and the samples half life is 3 days?
55) How long is the half life of an isotope if 2.0 grams of sample remain from a 64
gram sample after 30 years?
After having read through chapter 25, respond to these extension questions.
56) Element number 96 is named Curium. Do you think Marie and Pierre Curie did
enough in the advancement of science to have an element named after them?
Explain.
57) Thorium-231 is a radioactive isotope of thorium. It decays in ten steps to form
lead-207. The ten steps are:. Write this decay series.
Answers to Practice Problems
5) a. false b. true c. false d. false
6) a. true b. false c. true d. true
16) J. J. Thomson
17) Robert Millikan
18) 9.1 x 10-28 grams
19) Ernest Rutherford
20) Ernest Rutherford
21) Positive
22) James Chadwick
23) 1.67 x 10-24grams
24) 1.675 x 10-24 grams
35)
Isotope
Name
tin - 118
Symbol
118
Sn
40
+1
K
19
# p+
#e -
#no
50
50
19
Mass
Number
118
Charge
68
Atomic
Number
50
18
21
19
40
+1
9
10
10
9
19
-1
7
10
7
7
14
-3
52
52
76
52
128
0
0
50
Potassium-40
Fluorine -19
19
F -1
9
14
Nitrogen -14
7
N
-3
128
52
tellurium - 128
Te
43)Complete this chart on the three types of radioactive decay
Type
Alpha
Beta
Gamma
Symbol



44) (D)
52)
45) (B)
a.
Mass (amu)
4 amu
0 amu
0 amu
46) (B)
238
234
92
90
U
50) a.
4
Th + 2He
Charge
+2
-1
No charge
51) c
c. 222
218
86
84
Rn 
alpha
b.
F  -1  + 10Ne
19
9
0
19
alpha
d.
210
85
At  86 Rn +- 1 
Beta
53) Oxygen-17
4
Po + 2 He
210
0
beta
54) 6.25 g
55) 12 days
56) 6 years