Chemistry question bank
Grade
12ES
Subject
Chemistry
Chapter
24. Nuclear
Sections 24.1
Chemistry
1. Distinguish between the electrostatic forces (between
protons) and the nuclear forces (between neutrons and
protons) inside the nucleus
2. Explain why large nuclei are radioactive
3. Define radioactivity
4. Relate large and small nuclei stability with respect to the
ratio of neutrons to protons
5. Compare between the atomic number (Z)and mass
number(A) of a nucleus
Learning
Outcomes
6. Define isotopes and its notation 𝐴𝑍𝑋
7. Compare and contrast nuclear radiations( α, β-, β+, γ)
emitted from unstable nuclei in terms of nature, symbol,
mass, charge, penetration power
8. Write nuclear equations to predict the mass number and the
atomic number of a daughter nucleus when a parent nucleus
emits alpha, beta, or gamma radiations
9. Define half- life of a radioactive isotope
10.Calculate the remaining amount of radioactive element using
thr following mathematical formula
1
N = N ( 2 )n
Raseena Sajjad ATHS/ FUJ
Page 1
Multiple Choice Questions
1. A lightweight isotope is likely to be stable if the ratio of protons to
neutrons in its nucleus is(Outcome 4)
A
1:2.
B
1:1.
C
2:1
D
5:1
2. The only nucleon among the following is the(Outcome 1)
A
Positron
B
Neutron
C
electron
D
Beta particle
3. The isotope formed by the beta decay of
40
19K
has an atomic number
of(Outcome 6)
A
18
B
39
C
20
D
21
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4. The positron produced during positron emission comes from a(n)
(Outcome 7)
A
neutron.
B
proton
C
electron
D
positron
6. The decay of
A
2
B
-e
C
+e
D

162
Tm
69
yields
162
68Er
and (Outcome 8)
He4
8. The most penetrating form of nuclear radiation is(Outcome 7)
A
alpha rays
B
beta rays
C
gamma rays
D
positrons.
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9. In an atom, the strong nuclear force acts on(Outcome 1)
A
protons only
B
neutrons only
C
protons and neutrons
D
protons, neutrons, and electrons
10. The half-life of calcium-47 is about 5 days. Starting with 64 g of this
isotope, what would be the amount remaining after 20 days? (Outcome 10)
A
32 g
B
16g
C
8g
D
4g
11. A nuclear reaction may involve: (Outcome 1)
A
protons
B
neutrons
C
electrons
D
Protons& neutrons
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12. Unstable nuclei can break apart spontaneously, changing the identity of
the _____ . (Outcome 3)
A
elements
B
atoms
C
compounds
D
reactions
15. Alpha particles have a _____ charge. (Outcome 7)
A
-1
B
0
C
+1
D
+2
16. How does the nucleus of an atom change after a gamma irradiation?
(Outcome 8)
A
The atomic mass reduces by four and the atomic number reduces
by two.
B
The atomic mass remains the same, but the atomic number
increases by one.
C
The atomic mass remains the same, but energy is lost as the
nucleus decays.
D
The atomic mass changes by one, but the atomic number remains
the same.
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17. What is the reason for the decay of naturally radioactive elements?
(Outcome 8)
A
To reduce the number of neutrons as the elements lie above the
band of stability.
B
To reduce the number of protons as the elements lie below the
band of stability.
C
To reduce the number of either neutrons or protons to lie in the
band of stability.
D
To release the energy from nucleus in the form of gamma
radiation.
18. Compared to an electron, a positron has (Outcome 7)
A
the same mass and charge
B
the same charge
C
different mass and charge
D
the same mass, but a different charge
19. Identify the type of radiation that is produced when a neutron is
converted to a proton. (Outcome 7)
A
Alpha
B
Beta
C
Gamma
D
Positron
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21. Atoms with the same atomic number but different mass numbers are
(Outcome 6)
A
isomers
B
allotropes
C
isotopes
D
Isobars
Problems
1.Iron 59, a radioactive isotope, has a half life of 46 days. Calculate the
time by which 30.0 micrograms falls to 14% of the initial value in the body
of a cancer patient. (Outcome 10)
ANS ; 131 days
2. Calculate the remaining amount of 100.0 grams of cobalt-60 after 1600
years. The half life of cobalt-60 is 5272 years. (Outcome 10)
ANS ; 81.03 grams
3. 160.0 grams of radium 226 is reduced to 114.6 grams in 782 years. What
is the half life of the compound? (Outcome 10)
ANS: 1620 years
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4. Examine the figure provided and approximate the number of years in one
half life of strontium. (Outcome 9&10)
ANS: Aprox 25 yrs
5. Explain the following equation. (Outcome 10)
ANS:
N = remaining amount of radioactive element
No = initial amount of element
n = number of half lives that have passed.
6. An 80.0-g sample of a radioactive compound, radium-226, is reduced to
57.3 g in 782 years. What is the half-life of the compound? (Outcome 10)
ANS;, half-life
1620 years
8. Krypton-85 is used in indicator lights of appliances. The half-life of
krypton-85 is 11 y. How much of a 2.000-mg sample remains after 33 y?
(Outcome 10)
ANS; 0.25 mg
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9. The half-life of polonium-218 is 3.0 min. If you start with 20.0 g, how
long will it be before only 1.0 g remains? (Outcome 10)
Ans;13 min.
10. Technetium-99m is widely used in diagnosing medical problems. The
graph below shows the rate at which a 200-gram sample of technetium-99m
decays. Answer the following questions using the graph. (Outcome 9&10)
1. What is the half-life of technetium-99m?
The half-life is approximately 6 hr.
2.Estimate the amount of the original sample of technetium-99m that
remain
a. after 1 h;
180g
b. after 5 h; 120 g
Raseena Sajjad ATHS/ FUJ
c. after 10 h; 70g
d. after 1 day. 12 g
Page 9
3. Suppose that a doctor needs 25 g of technetium-99m in a medical
procedure, and a sample of 100 g is made at 8:00 A.M. What is the latest
time at which the procedure can be carried out? Why?
The latest time would be at roughly 8 P.M. the same day. Two half-lives, 6
hr. each, would have elapsed.
4. The technetium-99m is considered to be no longer useable when less than
6 g remains. At what time would the sample described in the preceding
question become unusable?
The sample would become unusable at roughly 8 A.M. the next day.
5. Radioactive isotopes used for medical purposes are usually produced in a
nuclear laboratory and shipped to hospitals. What problem can you see in
producing and using technetium-99m by this system?
The isotope may have decayed during shipping.
6. Technetium-99m decays in two steps, emitting first a gamma ray, then a
beta particle.
Answer the Following Questions
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1. Explain why the neutron-to-proton ratio of stable nuclei increases as the
atomic number increases (Outcome 4)
As atomic number increases, more and more neutrons are needed to
produce a strong nuclear force that is sufficient to balance the electrostatic
repulsion between protons.
2. Compare and contrast chemical reactions and nuclear reactions in terms
of energy changes and the particles involved. (Outcome 1)
Nuclear reactions release more energyper mole. Nuclear reactions involve
neutronsand protons, whereas chemical reactions involve electrons.
3. Define the band of stability and relate it to the value of the neutron-toproton ratio.
(Outcome 4)
The band of stability is the area on a graph showing the number of neutrons
versus the number of protons that contains all the stable nuclei. It
corresponds to a neutron-toproton ratio of 1:1 to 1.5:1 depending on the
atomic number.
4. Explain why radioisotopes above the band of stability are unstable.
(Outcome 4)
They are unstable because they have too many neutrons relative to their
number of protons.
7. Define the term half-life.
(Outcome 9)
A half-life is the time required for one-half of a radioisotope’s nuclei to decay
into its products.
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8. TheFigure shows alpha particles, beta particles, and gamma rays passing
through a screen and between two charged plates. What can you infer about
the identity of a, b, and c? Explain your answer. (Outcome 7)
A must be beta particles because their negative charge would cause them
to be deflected away from the negatively charged plate. B must be gamma
rays because they have no charge and would not be deflected by the
charged plates. C must be alpha particles because their positive charge
would cause them to be deflected away from the positively charged plate.
9. In which region(s) in Figure are you likely to find (Outcome 4)
a. stable nuclei?
b. nuclei that undergo alpha decay?
c. nuclei that undergo beta decay?
d. nuclei that undergo positron emission?
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10.Define Radioactivity.
(Outcome 3)
The spontaneous emission of radiation by an unstable atomic nucleus is
called Radio activity.
13.Complete the following nuclear equations. (Outcome 8)
a)
11
11
→
C
+
B
6
5
b)
238
4
-----
→
U
+
92
He
2
c)
14
14
C
6
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→
N
+
7
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d)
226
4
+
→
Ra
88
He
2
e)
15
15
O
→
8
Raseena Sajjad ATHS/ FUJ
N
+
7
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