Science 10
Name:______KEY_____________
Block:____ Date:______________
Chapter 7 Review
1. Radioactivity is the release of __high-energy____ particles and ___rays___ from a substance as a result of
changes in the nuclei of its atoms.
2. _Natural background radiation__ is the term for the radiation we come into contact with everyday that is
all around us. Generally, since this type of radiation is _always around us_, it is viewed as _harmless_.
3. List the different types of wave/rays in the electromagnetic spectrum from lowest frequency/energy to
highest frequency/energy.
Lowest Energy
Highest Energy
Radiowaves, microwaves, infrared rays, visible light, ultraviolet rays, x-rays, gamma rays
4. _Visible light____ is the one form of radiation that humans can actually see.
5. __Isotope______ is the term given to different atoms of a particular element that have the same number of
__protons______, but different numbers of __neutrons________.
6. The atomic number of an element is the same as the number of __protons________. The mass number of
an element represents the number of __protons____ and __neutrons____ added together.
7. Describe how you can find how many neutrons are in a certain isotope of an element if the atomic number is
52 and the mass number is 134.
 Since the atomic number = the # of protons, there are 52 protons in this isotope
 The mass number equals the # of protons + the # of neutrons.
 134 = 52 + # of neutrons
 So 134 – 52 = 82 neutrons
8. Standard atomic notation represents the __chemical symbol____, the __atomic number_____ and the
___mass number________ of a specific isotope.
9. Describe the element, atomic number, number of protons, mass number, and number of neutrons for the
41
K
following standard atomic notation: 19
 The element is potassium.
 The atomic number and number of protons is 19.
 The mass number is 41.
 The number of neutrons is 41 – 19 = 22
10. What do all isotopes of the same element have in common?

Isotopes of the same element have the same element name, atomic number and number of protons.
11. How do isotopes of the same element differ?

Isotopes of the same element have different mass numbers and different number of neutrons.
12. Complete the following table:
Isotope
Atomic Number
# of Protons
Mass Number
# of Neutrons
Carbon-13
6
6
13
7
Cobalt-59
27
27
59
32
Sodium-23
11
11
23
12
Arsenic-75
33
33
75
42
Chlorine-37
17
17
37
20
13. Radioactive atoms emit __radiation_________ because their nuclei are ___unstable______.
14. The process in which unstable nuclei lose energy (thus gaining stability) by emitting radiation is known as
____radioactive decay_____.
15. Isotopes that are capable of radioactive decay are called ___radioisotopes________.
16. The three main types of emitted radiation are __alpha____ radiation, ____beta____ radiation, and
__gamma____ radiation. This was first discovered by ___Ernest Rutherford_________.
17. Alpha radiation is a stream of __alpha particles_______ that have the same combination of particles as the
nucleus of a __helium_____ atom, with a mass number of __4__ and an atomic number of __2__.
18. Alpha particles are made up of __2___ protons and __2___ neutrons.
19. Alpha particles are much larger than other types of radiation making them relatively _slow__ and the least
_penetrating____ of the three types of radiation.
20. The term used to describe the emission of an alpha particle from a nucleus is ___alpha decay______.
21. Complete the following nuclear reactions involving alpha decay:

a)
208
84
Po 
204
82
Pb +
4
2
b)
225
89
Ac 
221
87
Fr +
4
2
c)
196
79
Au 
192
77
Ir +
He

4
2
22. A __beta particle_______ is an electron. Electrons have a negligible mass that is approximately 1/2000 the
mass of a proton or neutron, therefore electrons are assigned a mass of __zero (0)_.
23. Beta particles (electrons) have a charge of __-1______.
24. During beta decay a neutron changes into a __proton_________ and an __electron______. During this
process the __proton_______ stays in the nucleus while the __electron______ shoots out from the nucleus
with a significant amount of energy.
25. Since the only thing emitted during beta decay is an electron, the __mass number_____ remains unchanged
and the __atomic number___ increases by one.
26. Complete the following nuclear reactions involving beta decay:

6
3

14
7
N
Na 
24
12
a)
6
2
b)
14
6
C
c)
24
11
He
+
0
1
β
+
0
1
β
Mg +
0
1
Li
β
27. Gamma radiation consists of high __energy___ rays with a short _wavelength_______.
28. Gamma radiation has almost no __mass_______ and no __charge______, therefore during gamma decay
both the atomic number and mass number remain unchanged.
29. Gamma rays are one of the most __dangerous______ forms of electromagnetic radiation; they have much
more energy than either __X-rays_______ or _ultraviolet__ radiation.
30. Due to its insignificant size, __gamma radiation___ has the greatest __penetrating power______ of the
three major types of radiation. It would take a thick block of lead or concrete to stop it.
31. In gamma decay reaction equations we use the symbol (*) to represent that a certain nucleus has extra
__energy______.
32. Complete the following nuclear reactions involving gamma decay:
a)
60
28
Ni *

60
28
Ni +
0
0

b)
40
19
K*

40
19
K
+
0
0

c)
24
11
Na * 
24
11
Na +
0
0

33. The symbol  is used to represent an __alpha_____ particle, the symbol  is used to represent a
___beta_____ particle and the symbol  is used to represent a ___gamma______ ray.
34. Alpha particles can also be represented by a __helium________ nucleus, and beta particles can also be
represented by an __electron_____.
35. In nuclear equations, the __mass number____ and the atomic number remain __unchanged_______.
36. Carbon dating (also known as __radiocarbon dating______) is the process of determining the age of an
object by measuring the amount of __carbon-14_____ remaining in that object.
37. Describe the process of carbon dating. What is the maximum age of an object that can be determined by
carbon dating?
 Living objects have a nearly constant ratio between the carbon-12 and cabon-14 isotopes.
 Once an organism dies the ratio between the carbon-14 and carbon-12 isotopes decreases, which
allows us to determine the age of a dead object.
 Only objects that lived within the past 50,000 years can be used for carbon dating.
38. A half-life is a constant for any radioactive isotope and is equal to the time required for _half____ the
__nuclei____ in a sample to decay. For example, carbon-14 has a half-life of ___5730____ years,
radon-222 has a half-life of __3.8 ____ days and uranium-238 has a half-life of ___4.5____ billion years.
39. If the half-life for an isotope is 35 days, how much of a 10g sample would remain after:
a) 35 days? 5g
b) 70 days? 2.5g
c) 105 days? 1.25g
40. A decay curve is a curved line on a graph that shows the __rate_____ at which radioactive isotopes decay.
41. Explain how you would determine how much of a 50g sample of iodine-131 would remain if its half-life is
8 days and 32 days have passed since the sample was made?
 If 32 days have passed and iodine-131 has a half-life of 8 days, then 4 half-lives have passed:
(32days = 8days x 4half-lives).
 If the original sample was 50g: 50g x ½ x ½ x ½ x ½ = 3.125g
42. The isotope that undergoes radioactive decay is called the __parent isotope_______ and the stable product
of radioactive decay is called the ___daughter isotope______.
43. There are many common isotope pairs that exist. For example, the daughter isotope for carbon-14 is
__nitrogen-14_____ and the parent isotope for lead-207 is __uranium-235______.
44. Explain how we can use potassium-40 and argon-40 as a clock.
 Potassium-40 has a half-life of ~1.3 billion years and its daughter isotope is argon-40. When rock
is produced from lava there is no argon-40 gas present in the sample.
 As time passes some of the parent isotopes of potassium-40 are converted to argon-40 (and the
argon is trapped in the rock.) Specifically, every 1.3 billion years half of the potassium-40 isotopes
are converted to argon -40 isotopes.
 As the mass of the parent isotope drops, the mass of the daughter isotope increases. We can use
the ratio of these masses and compare them to a decay curve to determine how old a rock sample
is. (Essentially, the isotopes are acting like a clock.)
45. The two types of nuclear reactions include __fission_____ and ___fusion_____.
46. Nuclear fission involves the __splitting_______ of a larger nucleus into two smaller nuclei, subatomic
particles and energy. The fission of a nucleus is accompanied by a __very large_______ release of energy.
47. Larger, heavier nuclei tend to be __unstable___, and in order to increase stability, atoms with heavy nuclei
split into lighter atoms.
48. What are the downsides of performing fission reactions using nuclear reactors?
 Nuclear reactors produce wastes that need to be safely stored for very long periods of time.
 Nuclear reactors themselves also suffer significant deterioration.
 There is also concern that the nuclear material may be used in chemical warfare.
49. A nuclear reaction is a process in which the nucleus of an atom changes. This change occurs when the
nucleus __gains____ or __releases__ particles or energy. A small change in mass during nuclear reactions
results in a large change in __energy______.
50. Nuclear reactions are quite remarkable. A fission reaction involving just __one__ gram of uranium-235
releases the same amount of energy as burning ___two tonnes___ of coal!
51. Scientists have also developed methods in forcing nuclear reactions to occur. The term for this type of
nuclear reaction is an ___induced nuclear reaction____. During these forced reactions, a nucleus is
__bombarded_______ with alpha particles, beta particles, or gamma rays.
52. Describe the process of the induced uranium-235 nuclear fission reaction that occurs in both fission-style
nuclear weapons and in Canadian nuclear power plants. Be sure to include the production of the unstable
uranium-236 isotope in your explanation, as well as all the reactants and products of the reaction.
 During the nuclear fission reaction of U-235, a U-235 atom is bombarded with a neutron.
 The nucleus of the uranium-235 absorbs the neutron, increasing the mass number by one and
creating the unstable uranium-236 isotope.
 The unstable uranium-236 isotope then undergoes a nuclear fission reaction, splitting the unstable
U-236 into smaller nuclei (krypton-92 & barium-141), 3 neutrons, and a large amount of energy.
53. Why is the release of neutrons, krypton-92 and barium-141 in the induced uranium-235 reactions important?
 The release of neutrons in the U-235 reaction is important because the neutrons trigger more
fission reactions to occur. Each reaction produces 3 neutrons which can cause three additional
fission reactions and start a large chain reaction.
 Krypton-92 and barium-141 are unstable products and can further decay into other isotopes
releasing more useful energy.
54. The term used to describe the ongoing process in which one reaction initiates another or more reactions is a
_chain reaction_____. These types of reactions can produce increasingly rapid amounts of __energy___
and may lead to __violent______ nuclear explosions.
55. Chain reactions can be controlled using ___cadmium rods_____ to absorb neutrons.
56. Explain why chain reactions are a concern in nuclear power plants.
 Chain reactions can be controlled using materials that absorb neutrons. However, a concern
about nuclear power plants is that the nuclear reactions may race out of control. So precise
monitoring and adjusting must be done to ensure the nuclear reactors remain under control and
do not release harmful levels of radiation or worse, cause an explosion.
57. Explain what CANDU stands for, how it works and why it is a modern leader in the nuclear technology of
the world.
 CANDU stands for CANadian Deuterium Uranium reactor. The reactor is one of the safest
nuclear reactors in the world and can be shutdown quickly if problems arise.
 CANDU reactors produce a lot of heat which is used to drive turbines that produce electricity,
further increasing the efficiency of the energy plant.
58. The fuel used in CANDU reactors comes in the form of __bundles of rods___ containing uranium pellets.
Once used, they are placed deep underground in __stable____ rock formations.
59. Nuclear fusion is the process in which __two_ low mass nuclei join together to form a more _massive___
nucleus. This type of reaction occurs on the __sun_____, as well as on other ___stars___.
60. Fusion reactions require a tremendous amount of ___temperature____ and ___pressure______ to occur.
61. Describe the fusion reaction that occurs in the Sun.
 At the core of the sun a deuterium and a tritium combine to form a helium atom, a neutron and a
lot of energy.
 21 H + 31 H  42 He + 01 n + energy
62. What do fission and fusion reactions have in common?
 Both fission and fusion reactions release large amounts of energy.
 They are both used in nuclear weapons.
63. How do fission and fusion reactions differ? Be sure to consider the reactants, the products, and human
usage.
 Fission reactions involve a heavy unstable nucleus splitting apart to form 2 smaller nuclei, while
fusion reaction involve combining two smaller nuclei to form a heavier nucleus.
 Fission reactions often produce daughter products that are also radioactive, while fusion reactions
usually do not produce radioactive products.
 Fission reactions are common in nuclear power plants, while fusion reactors have still not been
made (due to the high temperature and pressure required and the tremendous amount of heat
produced is difficult to contain)
 Fusion reactions can occur in nuclear weapons, but fission reactions must also occur in the same
weapon to produce the temperature and pressure needed for the fusion reaction to occur.
Vocabulary to Know:
Write a concise definition of each of these terms found in this chapter.
Alpha decay:
Hazardous wastes:
Alpha particle:
Induced nuclear reaction:
Beta decay:
Isotopes:
Beta particle:
Light:
CANDU:
Mass number:
Chain reaction:
Nuclear equation:
Daughter isotope:
Nuclear reaction:
Decay curve:
Parent isotope:
Fission:
Potassium-40 clock:
Fusion:
Radiation:
Gamma decay:
Radioactive decay:
Gamma ray:
Radiocarbon dating:
Half-life: