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Radioactivity Flashcards

(101 cards)

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1
Q

When did Becquerel observe that a crystal of uranium salt spontaneously emitted radiation?

A

“1896”

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2
Q

What did Becquerel’s observation penetrate through?

A

“Opaque material”

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3
Q

What did the radiation from the uranium salt affect?

A

“A photographic plate”

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4
Q

What metal and its compounds possessed the same property of emitting radiation?

A

“Uranium”

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5
Q

What did Becquerel call the phenomenon of uranium emitting radiation?

A

“Radioactivity”

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6
Q

What element did Pierre and Marie Curie detect radioactivity in in 1898?

A

“Thorium”

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7
Q

What was the uranium ore called that had a higher level of radiation than could be explained by its uranium content?

A

“Pitchblende”

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8
Q

What radioactive elements did Pierre and Marie Curie isolate from pitchblende?

A

“Polonium and radium”

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9
Q

How much more radioactive was radium than the same mass of uranium?

A

“Several million times”

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10
Q

How many naturally occurring radioactive substances have been found since the Curies’ discoveries?

A

“More than 40”

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11
Q

What kind of reactions could not explain radioactivity?

A

“Ordinary chemical reactions”

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12
Q

What part of the atom could explain radioactivity?

A

“The nuclei”

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13
Q

What is radioactivity?

A

“The spontaneous emission of radiation by an element”

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14
Q

What is a radioactive element?

A

“An element that emits radiation”

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15
Q

Give an example of stable and radioactive isotopes of carbon.

A

”${}^{12}C$ and ${}^{14}C$ respectively”

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16
Q

What are the characteristics of radioactivity?

A

“A radioactive substance emits radiation continually and spontaneously

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17
Q

What can radioactive radiation penetrate through?

A

“Opaque matter”

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18
Q

What does radioactive radiation affect, like visible light rays?

A

“Photographic plates”

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19
Q

What does radioactive radiation do to gases?

A

“Ionizes them”

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20
Q

What phenomenon does radioactive radiation cause in certain substances like zinc sulphide?

A

“Fluorescence”

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21
Q

What does radioactive radiation leave in a cloud chamber?

A

“Tracks”

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22
Q

What is radioactivity always associated with?

A

“A release of energy”

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23
Q

How much greater is the energy of radioactivity compared to that liberated during any chemical reaction?

A

“About a million times as great”

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24
Q

What is the energy of radioactivity known as?

A

“Nuclear energy”

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25
What are the three main components of radioactive radiation?
"Alpha- (α-)
26
How can the three components of radioactive radiation be separated and distinguished?
"By their behaviour in an electrostatic field"
27
What is an alpha-ray?
"A fast-moving stream of positively charged particles
28
What is an alpha-particle equivalent to?
"A helium nucleus
29
Which plate in an electrostatic field are alpha-particles deflected towards?
"The negative plate"
30
What is the penetrating power of alpha-rays?
"Very low"
31
What can stop or absorb alpha-rays?
"A thin sheet of paper or an aluminium foil which is only 0.1 mm thick."
32
What kind of effect do alpha-rays exert upon any gas they pass through?
"A very powerful ionizing effect"
33
What can alpha-rays cause in some materials, e.g. zinc sulphide?
"Fluorescence"
34
What are beta-rays?
"Very fast-moving streams of electrons"
35
Which plate in an electrostatic field are beta-rays deflected towards?
"The positive plate"
36
What is the mass number and charge of a beta particle?
"A mass number of zero and a charge of -1"
37
How is a beta particle represented?
"The symbol $-1^{0}e$"
38
How does the penetrating power of beta-rays compare to alpha-rays?
"Beta-rays are much more penetrating than alpha-rays"
39
What is the range of beta-rays in air?
"About 3 m"
40
What is the range of beta-rays in aluminium?
"About 4 mm"
41
How does the ionization power of beta-particles in air compare to alpha-particles?
"It is only about one-thousandth of that of alpha-particles"
42
What can beta-rays cause fluorescence in?
"Certain substances like anthracene"
43
Can beta-rays cause fluorescence in zinc sulphide?
"No"
44
What are gamma-rays?
"Electromagnetic waves similar to visible light and X-rays
45
What is the speed of gamma-rays?
"The speed of light"
46
Are gamma-rays affected by an electrostatic field?
"No"
47
How does the ionization power of gamma-rays compare to alpha- and beta-rays?
"They have the least ionization power"
48
How does the penetrating power of gamma-rays compare to alpha- and beta-rays?
"They are the most penetrating"
49
How far can gamma-rays penetrate through air?
"About 100 m"
50
What thickness of iron or lead can gamma-rays pass through?
"0.5 m"
51
What substances can gamma-rays cause fluorescence in?
"Substances like sodium iodide and zinc sulphide."
52
What are X-rays?
"Electromagnetic waves
53
How are X-rays produced?
"By allowing fast-moving electrons to bombard metals such as tungsten."
54
What do fast-moving electrons do to metal atoms?
"Knock electrons out of the inner shells"
55
What replaces the dislodged electrons?
"Electrons moving in from the outer shells."
56
What accompanies the movement of electrons that replace dislodged electrons?
"The emission of X-rays"
57
What can X-rays penetrate easily through?
"Most solid substances which are opaque to visible light
58
Which have greater penetrating ability: hard X-rays or soft X-rays?
"Hard X-rays"
59
What are soft X-rays used for in medicine?
"To photograph human body parts."
60
What are hard X-rays used for?
"Destroying cancerous cells."
61
What are X-rays used for in chemistry?
"To study the arrangement of particles in crystal lattices and in big organic molecules like proteins."
62
What are some of the devices developed for detecting radiation?
"The Geiger-Muller counter
63
What is the Geiger-Muller counter based on?
"The ionizing effect of radiation on gases."
64
What does the Geiger-Muller counter consist of?
"An ionization chamber with two metal electrodes
65
What is the potential difference maintained between the electrodes in a Geiger-Muller counter?
"About 450 volts"
66
What happens when an ionizing particle or radiation enters the chamber of a Geiger-Muller counter?
"Some argon atoms are ionized."
67
What happens to the electrons and positive ions produced when argon atoms are ionized?
"The electrons drift to the positive terminus while the positive ions migrate to the negative one."
68
What is obtained for a short while when ions are produced in a Geiger-Muller counter?
"A small current
69
How is the current in a Geiger-Muller counter detected?
"By suitable equipment
70
What is the Geiger-Muller counter widely used for?
"Detecting radioactivity."
71
What can the Geiger-Muller counter also be used to measure?
"The intensity of radiation."
72
What is proportional to the intensity of the radiation?
"The count rate"
73
What do certain minerals, such as zinc sulphide, do when exposed to radiation?
"Fluoresce or glow"
74
What is the glow from minerals like zinc sulphide made up of?
"Tiny flashes of light or scintillations"
75
How can scintillations be seen or counted?
"Under a microscope or with a suitable device."
76
What is the diffusion cloud chamber used for?
"Detecting the actual paths followed by individual a- and β-particles."
77
What are the ionizing particles allowed to pass through in a diffusion cloud chamber?
"A gas which has been supersaturated with water vapour."
78
What do the ions formed in the track of the ionizing particles act like?
"Dust
79
What is revealed as a result of the ions in a diffusion cloud chamber?
"The path of the particle as a visible vapour trail."
80
How can a permanent record of the movements of alpha- or beta-particles be obtained?
"By photographing the tracks."
81
What is radioactivity?
"The spontaneous disintegration of the nucleus of an atom."
82
What word is used to describe when a certain quantity of a radioactive material disintegrates spontaneously?
"Decay"
83
What is emitted during disintegration of a radioactive atom?
"Either an α-particle or β-particle."
84
What may accompany the emission of alpha- or beta-particles?
"Gamma-rays"
85
What happens to the parent nucleus during radioactive decay?
"It undergoes a change in atomic number and becomes the nucleus of a different element."
86
What is the new nucleus called?
"The daughter nucleus"
87
What is the process of forming a new nucleus called?
"The transmutation of an atom."
88
Is radioactive decay a random or predictable process?
"Random"
89
What does the rate of decay depend on?
"The radioactive material"
90
Does the rate of decay vary widely?
"Yes"
91
Can any physical or chemical process alter or affect the rate of disintegration of atoms?
"No"
92
What kind of law does the disintegration of an element follow?
"An exponential law"
93
What happens to the atomic number of an atom when it loses an α-particle during disintegration?
"It is reduced by two units."
94
What happens to the mass number of an atom when it loses an α-particle during disintegration?
"It is reduced by four units."
95
Where is the new element formed in alpha decay placed in the Periodic Table?
"Two places to the left of the original element."
96
How can alpha decay be represented?
"$\begin{matrix}A\\ z\end{matrix}X\rightarrow\begin{matrix}(A-4)\\ (Z-2)\end{matrix}Y+\begin{matrix}4\\ 2\end{matrix}He$"
97
In the alpha decay equation, what do X and Y represent?
"Parent nucleus and daughter nucleus respectively"
98
What is an alpha particle equivalent to in the alpha decay equation?
"A helium nucleus (${}_{2}He$)"
99
If a uranium nucleus, ${}_{92}^{238}U$, emits an α-particle, what does it change to?
"The nucleus of a new element
100
How do the atomic and mass numbers of thorium-234 compare to uranium-238?
"They are smaller by two and four units respectively."
101
Where is thorium found in the Periodic Table relative to uranium?
"Two places to the left"

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