Radioactivity Flashcards
(155 cards)
1
Q
What is the charge of a proton?
A
+1
2
Q
What is the relative mass of a proton?
A
1
3
Q
What is the charge of a neutron?
A
0
4
Q
What is the relative mass of a neutron?
A
1
5
Q
What is the charge of an electron?
A
-1
6
Q
What is the relative mass of an electron?
A
1/1835
7
Q
What is the mass number?
A
Total number of protons and neutrons
8
Q
What is the atomic number?
A
Number of protons (and electrons)
9
Q
Number of protons = …?
A
Number of electrons
10
Q
Top number of an element
A
Atomic mass number (always the bigger number)
11
Q
Bottom number of an element
A
Atomic number
12
Q
What is an isotope?
A
Atoms of the same element with the same number of protons but different number of neutrons
(Different mass numbers)
13
Q
How many element’s isotopes are stable?
A
Only one or two
14
Q
What is radioactive decay?
A
The unstable isotopes decay by emission of high energy particles or waves to become more stable
15
Q
What can electrons do if they gain enough energy?
A
Jump to a higher energy level (shell)
16
Q
Where do electrons get the energy from to jump to a higher energy level (shell)?
A
Electromagnetic radiation
17
Q
What happens soon after an electrons jumps to a higher energy level?
A
Fall back down to the lower energy level
18
Q
What will the electron re-emit when it falls back down to the lower energy level?
A
Re-emit the energy as electromagnetic radiation
19
Q
What is an ion?
A
An atom which has a charge because it has either lost or gained electron (s)
20
Q
Loss of electron = …?
A
Positive ion
21
Q
Gain of electron = …?
A
Negative ion
22
Q
What does ionising radiation mean?
A
Able to knock electrons off atoms and so ionise them
23
Q
What is alpha made up of?
A
2 protons
2 neutrons
24
Q
What is the overall charge of an alpha particle?
A
2+
25
Are alpha particles small or big?
Relatively large - easily stopped by collisions with other molecules
26
How far can alpha penetrate?
Not very far:
A few cm in the air
Absorbed by a single sheet of paper
27
Are alpha particles weak or strongly ionising?
Strongly ionising - easily knock electrons off of any atoms they collide with
28
What are beta particles made up of?
Electrons
29
What is the charge of beta particles?
-1
30
Do beta particles have a mass?
No
31
How far can beta particles penetrate?
Far:
Several metres of air
5mm of aluminium or Perspex
32
Are beta particles weak or strongly ionising?
Weak/low ionising power
33
What are gamma rays?
Waves of electromagnetic radiation
(Pure energy)
34
When is gamma radiation often emitted?
After alpha or beta radiation
35
Why is gamma radiation often emitted after alpha or beta radiation?
A way of the nucleus getting rid of extra energy
36
Do gamma rays have a mass?
No
37
Do gamma rays have a charge?
No
38
How far can gamma rays penetrate?
Really far into materials:
Long distances through air
Thick sheet of lead or concrete needed to stop them
39
Are gamma rays weak or strongly ionising?
Very weak/low ionising power
40
What is the emission of a neutron?
Nucleus contains too many neutrons (unstable)
—> can throw out a neutron to make it more stable
41
Nuclear decay equation for alpha
4
He
2
42
Nuclear decay equation for beta
0
B/e
-1
43
Nuclear decay equation for gamma
0
Y
0
44
Nuclear decay equation for neutrons
1
n
0
45
What is background radiation?
The low-level ionising radiation in the environment which is always present
46
Background radiation: radon gas %
50%
47
Background radiation: ground and buildings %
14%
48
Background radiation: medical %
14%
49
Background radiation: food and drink %
11.5%
50
Background radiation: cosmic rays %
10%
51
Background radiation: nuclear power %
0.3%
52
What does a Geiger-Müller tube do?
Counts the number of particles/waves over a fixed time period
53
Equation for count rate
Number of counts
—————————
Time
54
What is the count rate measured in?
Becquerels, Bq
55
What 2 things can you use to detect radiation?
Geiger-Müller tube
Photographic film
56
What is the source of a beta particle?
A neutron decaying into a proton and an electron
57
What is activity?
The overall rate at which unstable nuclei decay
58
What is activity measured in?
Becquerels
59
1bq = …?
1 decay per second
60
The activity of a radioactive isotope …?
Decreases over time
61
Why does the activity of a radioactive source decrease over time?
As more unstable nuclei decay, the number of unstable nuclei decreases, so fewer decays happen per second
—> causes the activity to decrease over time
62
What does half-life mean?
1) the time taken for the activity or number of decays to halve
2) the time taken for the number of radioactive nuclei in a sample to half
63
Fewer radioactive nuclei = …?
A lower activity
64
What is irradiation?
The process by which objects are exposed to any type of radiation
65
What are the ionising radiations?
Alpha
Beta
Gamma
X-ray
66
What are the non-ionising radiations?
Ultraviolet
Microwave
67
What is more dangerous: ionising or non-ionising radiation?
Ionising
68
What is contamination?
When radioactive particles get into other objects
69
What determines how harmful radiation is?
Type of radiation
Where your exposed to it (internally or externally)
The amount of radiation
70
What can ionising radiation enter?
Living cells and interact with the molecules inside
71
What can radiation do to our DNA?
Ionise it which can cause mutations
72
What happens in rare cases if radiation mutates your DNA?
Lead to the cells dividing uncontrollably and develop cancer
73
What other type of radiation can also lead to cancer?
Ultraviolet
74
Most harmful radiation —> not harmful radiation (list)
Alpha
Beta
Gamma
X-rays
Ultraviolet
Visible light
Infra-red
Microwave
Radiowaves
75
What determines the amount of radiation you’re exposed to?
How far away from the source you are
How long you’re exposed to it
How radioactive that substance is
76
How can you minimise radiation (safety precautions)?
Wear protective gloves and overalls
Use long tongs
Wear goggle
Wear a dosimeter
Point away from body
Keep in a lead-lined box
Keep in a locked cupboard
77
How can radiation be used to detect a water leak?
1) the source of gamma radiation is put into the water and is being used as a tracer
2) a Geiger-Müller tube is used to locate the point where the radiation is the highest
3) where the water leaks into the ground, there will be more radiation given off
78
Which radiation is used for the thickness of kitchen foil?
Beta particles
79
Why are beta particles used for making the thickness of kitchen foil (aluminium)?
They can penetrate the foil but some particles will be absorbed
80
What does the number of beta particles that are absorbed depend on (aluminium)?
The thickness of the foil
81
What happens if the foil leaving the rollers is too thick?
Fewer beta particles will reach the detector and so the pressure on the rollers with be increased
82
What happens if the foul leaving the rollers is too thin?
More beta particles will reach the detector and so the pressure on the rollers will be reduced
83
What do smoke alarms include a source of?
Alpha particles
84
Why doesn’t the alpha in smoke alarms cause any harm to the people living in the house?
The particles do not penetrate far
—> will be absorbed by the packaging or a few cm of air
85
What happens to a smoke alarm when there is no smoke?
Alpha particles ionise the air inside the alarm
The charged particles allow a current to flow between the two electrodes
86
What happens to a smoke alarm when there is smoke?
The smoke particles slow down the movement of the ions
This makes the current fall and the alarm sounds
87
What two ways is radiation used in medicine?
Radiotherapy
Medical tracers
88
What happens if our cells receive a large enough dose of radiation?
They can be killed off completely
—> radiation sickness
89
What is radiotherapy?
The use of targeted doses of radiation to kill cancerous cells
90
Where can radiotherapy be?
Internally or externally
91
Which radiation is used for external radiotherapy?
Gamma rays
92
How are gamma rays used in external radiotherapy?
They are targeted at the cancer site from lots of different angles so that only the cancer site gets the highest dosage
93
Which radiation is used for internal radiotherapy?
Beta
94
How is beta radiation used in internal radiotherapy?
Source is placed inside the body either inside or next to the cancer
95
What are the side effects of radiotherapy?
Healthy cells will also get damaged or killed
—> why cancer therapy often makes patients feel so ill
96
Where are medical tracers used?
Placing certain radioactive isotopes inside a person’s body by either injecting them or swallowing them
97
How do medical tracers work?
We can track the movement of the isotopes around the body by tracking the radiation they emit
98
What can we check are working with medical tracers?
Organs
99
How do we check to see if organs are working properly with medical tracers?
By seeing if they absorb the right amount of the substance
100
Which radiation is used for medical tracers?
Gamma rays
101
Why are gamma rays used for medical tracers?
They are less harmful than alpha and beta
102
In medical tracers what do we want the isotopes to have?
As short half-life as possible
103
Why do we want to use isotopes with as short half-life as possible?
So they only emit radiation for a short period while you take the measurements
—> then they stop being harmful
104
Pros of medical tracers
Help diagnose diseases
—> worth the risk
105
How can you minimise the risk of medical tracers?
Low dose
Short half-life
106
Pros of radiotherapy
Save a person’s life
—> worth the side-effects
107
Why do some people choose not to do radiotherapy?
Not worth the risks if they are only adding on a bit of time to their life rather than saving their life
108
What is nuclear fission?
The splitting up of large unstable nuclei into smaller nuclei
109
What does fission release loads of?
Kinetic energy
110
How do we get all of our nuclear energy on Earth?
Nuclear fission
111
When can nuclear fission occur?
Spontaneously: fission is unforced and happens itself (rare)
Absorbing a neutron: which can split a nucleus by making it even less stable
112
What do we use to get the process of fission started in nuclear reactors?
Neutrons
113
What is a chain reaction?
The sequence of reactions produced when a nuclear fission reaction triggers one or more further fissions
114
What is alpha radiation used for?
Smoke detectors
115
What is beta radiation used for?
Monitor thickness of paper/aluminium
116
What is gamma radiation used for?
Sterilise surgical instruments
Preserve food
Detecting underground leaks
117
What health problems can be caused by radiation?
Mutations to DNA
Skin burns
Cancer
118
What does a dosimeter do?
Measures the amount of exposure to radiation
119
What happens if nuclear fission is not controlled properly?
The whole system can quickly get our of control
—> release huge amounts of energy
—> what happens in nuclear bombs
120
What controls the rate of fission in nuclear reactors?
Control rods
121
What is a control rod?
Lowered into the reactor to absorb neutrons to control the rate of reaction
122
What is the control rod made from?
Boron
123
What is a fuel rod?
Provides material for fission
124
What is a moderator?
Slows the neutrons down so they can be absorbed by the nuclei
E.g. heavy water
125
What is the moderator made from?
Graphite
126
What is shielding (nuclear reactors)?
Prevents irradiation of workers
127
What is a coolant?
Transfer thermal energy from the rods to the heat exchanger
E.g. water
128
What is the energy released from nuclear reactors used for?
To heat up water and turn it into steam
—> which can then drive turbines that are connected to an electricity generator
129
Pros of nuclear reactors
Uranium and plutonium fuel is relatively cheap
Produces a large and steady amount of fuel
Not renewable energy but it is clean
Doesn’t produce green house gases like fossil fuels do
130
Cons of nuclear reactors
Nuclear power plants are very expensive to build
The nuclear waste they produce is expensive to get rid of
—> has to be buried underground in special bunkers
Always a risk of a major disaster if the plant malfunctions
—> very unlikely
—> but makes people suspicious of using nuclear energy
131
What is nuclear fusion?
When two lighter nuclei join/fuse to form a single larger nuclei
132
What does nuclear fusion release tons of?
Energy (more than nuclear fission)
133
In nuclear fusion what do the hydrogen nuclei form?
Helium
134
Is the helium atoms lighter or heavier than the two hydrogen nuclei?
Lighter
135
Why is the helium nuclei lighter than the two hydrogen nuclei?
Some of the mass is converted to energy
136
Why is so much energy released in nuclear fusion?
Some of the mass is converted to energy
137
What process fuels stars?
Nuclear fusion
138
How were all elements heavier than hydrogen made?
By nuclear fusion
139
What does nuclear fusion not produce?
Any radioactive waste
—> we can easily make the hydrogen that’s needed as fuel
140
What does fusion only occur in?
Really high temperatures and pressure
10,000,000 degrees celsius
141
Where does fusion occur?
Stars
142
Why can’t nuclear fusion be done on earth/why does it only happen at really high temperatures and pressure?
Fusion requires lots of energy for the two nuclei to fuse as they are both positively charged and so they repel
143
What does the unstable ‘parent’ nuclei split up into?
Two ‘daughter’ nuclei and two or three neutrons
144
What is the unstable nuclei called (pre fission)?
‘Parent’ nuclei
145
Why are gamma rays used to detect water leaks?
They are the most penetrating and so they can penetrate the ground
146
Why is alpha radiation used in smoke alarms?
It is the most ionising so it will ionise the air
147
If you’re irradiated what can’t you do?
Emit that radiation to others
148
If your contaminated what can you do?
Harm others
149
Which radiation is the most harmful inside your body?
Alpha
150
Why is alpha radiation the most harmful inside your body?
It is the most ionising
151
What is the most dangerous radiation outside the body?
Gamma
152
What happens to photographic film when it is exposed to radiation?
It becomes darker
153
What do unstable nuclei undergo?
Radioactive decay
154
Radioactive decay is …?
Random and spontaneous
155
What does spontaneous mean?
Not influenced by external or environmental factors
