Radioactivity Flashcards
1
Q
What is the approximate radius of an atom?
A
around 1×10-10 metres.
2
Q
What is an atom?
A
atom
The smallest part of an element that can exist.
3
Q
What defines an element?
A
The number of protons
4
Q
What is the mass number?
A
The number of protons and neutrons found in the nucleus of an atom.
5
Q
What is the atomic number?
A
The number of protons in the nucleus of an atom. Also called the proton number.
6
Q
What can mass number also be called?
A
The nucleon number
7
Q
What can the atomic number also be called?
A
The proton number
8
Q
What happens when an atom becomes ionised?
A
number of electrons will change
9
Q
What is an ion?
A
An ion is an atom that has lost or gained one or more electrons.
10
Q
What did the Ancient Greek philosopher Demokritos think that matter was?
A
thought that matter was made up of millions of tiny, uncuttable pieces of that same matter
11
Q
Where does the word atom come from?
A
Comes from the word atomos which means uncuttabls
12
Q
Who discovered the electron?
A
J J Thomson
13
Q
What year did J J Thomson discover the electron?
A
In 1897
14
Q
What did J J Thomson propose about the atom?
A
proposed that the atom looked like a
plum pudding
15
Q
What is the plum pudding model?
A
The scientific idea that an atom is a sphere of positive charge, with negatively charged electrons in it.
16
Q
What was the evidence available to Thomson at the time he discovered the plum pudding model?
A
1.solids cannot be squashed, therefore the atoms which make them up must be solid throughout
2.rubbing two solids together often results in static charge so there must be electrons on the outsides of atoms which can be transferred as atoms collide
17
Q
Who did an experiment to test the plum pudding model?What year was the experiment carried out?
A
In 1905, Ernest Rutherford with his 2 students Hans Geiger and Ernest Marsden
18
Q
How did Rutherford test the plum pudding model?
A
They directed a beam of alpha particles at a very thin gold leaf suspended in a vacuum
19
Q
What are alpha particles a form of?
A
Nuclear radiation with a large positive charge
20
Q
Why was the vacuum important when testing the Plum pudding model?
A
any deflection of the alpha particles would only be because of collisions with the gold foil and not due to deflections off anything else.
21
Q
What did they expect the alpha particle to do when testing the Plum Pudding model?
A
It was thought that the alpha particles could pass straight through the thin foil, or possibly puncture it
22
Q
What did they actually find when then tested the Plum pudding model?
A
1.most of the alpha particles did pass straight through the foil
2.a small number of alpha particles were deflected by large angles (> 40°) as they passed through the foil
3.a very small number of alpha particles came straight back off the foil
23
Q
The fact that most alpha particles went straight through the foil is evidence for? (PP model)
A
the atom being mostly empty space
24
Q
What does A small number of alpha particles being deflected at large angles suggest? (PP model)
A
there is a concentration of positive charge in the atom. Like charges repel, so the positive alpha particles were being repelled by positive charges.
25
What does The very small number of alpha particles coming straight back suggest? (PP model)
the positive charge and mass are concentrated in a tiny volume in the atom (the
nucleus
).
26
What does the positive charge and mass are concentrated in a tiny volume mean?
the chance of being on that exact collision course was very small, and so the ’target‘ being aimed at had to be equally tiny.
27
What had Rutherford discovered about the atom?
the nuclear atom, a small, positively-charged nucleus surrounded by empty space and then a layer of electrons to form the outside of the atom.
28
Who made the discovery of the make-up of the nucleus?
It came much later, and was not made by Rutherford
29
What size was the nucleus Calculated to be after Rutherfords experiment?
about 1/10,000th the size of the atom.
30
How can an atoms nucleus only be stable?
if it has a certain number of
neutrons
for the number of
protons
it has
31
How stable are elements with fewer protons?
the ones near the top of the
periodic table
, are stable if they have the same number of neutrons and protons,
32
What happens to the stability of the Nucleus as the number of protons increase?
More neutrons are needed to keep the nucleus stable
33
What happens to nuclei with too many or too little Neutrons
unstable and will
decay
, in a random process, emitting
radiation
.
34
What is radiation?
Energy carried by particles from a radioactive substance, or spreading out from a source.
35
What is radioactive decay?
The process in which unstable atomic nuclei break apart or change, releasing radiation as they do so.
36
An unstable
nucleus
can decay by emitting what?
1.an alpha particle
2.a ß- (beta minus) particle
3.a ß+ (positron)
4. a gamma ray
or in some cases a single
neutron
.
37
If the nucleus is unstably large what will it emit?
an alpha particle.
38
What is an alpha particle?
a 'package' of two protons and two neutrons
39
What nucleus does an alpha particle contain?
An alpha particle is also a helium-4 nucleus
so it is written as 4
2He. It is also sometimes written as 4
2α.
40
What does alpha decay do to the mass and atomic number?
It causes the mass number
of the nucleus to decrease by four
and the atomic number
of the nucleus to decrease by two.
41
What happens if the nucleus has too many neutrons?
neutron will turn into a beta minus (β-) particle-known as beta radiation
42
What is a beta minus (β-) particle?
neutron will turn into a proton and emit a fast-moving
electron
.
43
What is the relative mass and mass number of a beta particle?
0 for both
44
What is a beta particle a electron,neutron or proton?
An electron so written as 0
-1e. However, sometimes it is also written as 0
-1β.
45
Where has the beta particle come from in the atom?
The beta particle is an electron but it has come from the nucleus, not the outside of the atom.
46
What can neutrons be split into?
neutrons can split into a positive proton (same mass but positive charge) and an electron (which has a negative charge to balance the positive charge)
47
What happens to the neutron once it has been split?
It is then ejected at high speed and carries away a lot of energy.
48
What does beta decay do to the atomic and mass numbers?
Beta decay causes the atomic number of the nucleus to increase by one and the mass number remains the same.
49
What will happen if a nucleus has too few neurons?
A proton will tern into a beta plus (β+) particle
50
What is a beta plus (β+) particle?
proton will turn into a neutron and emit a fast-moving positron- this is called positron emission
51
What is a positron?
A positron is the antimatter version of an electron
52
Describe the mass number and relative atomic mass number of a positron..
has the same relative mass of zero, so its mass number is zero, but a +1 relative charge.
53
How is a positron written?
can be written as 0
+1e, however sometimes it is also written as 0
+1β.
54
What does beta plus decay do to the atomic number?
It causes the atomic number of the nucleus to decrease by one and the mass number remains the same.
55
What can move the nucleus to a lower energy state?
A re-arrangement of the particles in a nucleus
56
What happens to the difference in energy when particles are rearranged inside of the nucleus?
The difference in energy is emitted as a very high frequency
electromagnetic wave
called a
gamma ray
.
57
What is an electromagnetic wave?
A transverse wave caused by oscillations in an electromagnetic field.
58
What happens to the nucleus after emitting an alpha or beta particle?
the nucleus will often still have excess energy and will again lose energy. A nuclear re-arrangement will emit the excess energy as a gamma ray.
59
How goes gamma ray emission effect the atomic number and mass number?
change in the number of particles in the nucleus meaning both the atomic number and mass number remain the same.
60
Occasionally what is possible for a neutron to be emitted by?
radioactive decay
61
How can a neutron be emitted by radioactive decay happen?
can occur naturally
Or
occur artificially
62
What does neutron emission do to the mass and atomic number?
Neutron emission causes the mass number of the nucleus to decrease by one and the atomic number remains the same.
63
How are The different types of radiation are often compared?
In terms of their:
1.penetrating power
2.their ionising power
3.how far they can travel in the air.
64
What is penetrating power?
The power of the radiation that demonstrates how far into a material the radiation will go.
65
What is the penetrating power of an alpha particle?
Skin/paper
66
is the ionising power of an alpha particle high or low?
High
67
What is the range in air for an alpha particle?
< 5 centimetre
68
What is the penetrating power for a beta particle?
3mm aluminium foil
69
is the ionising power for a beta particle high or low?
Low
70
What is the range in air for a beta particle?
≈ 1 metre (m)
71
What is the penetrating power for a gamma particle?
Lead/concrete
72
is the ionising power for a gamma particle high or low?
Very low
73
What is the range in air for a gamma particle?
> 1 kilometre (km)
74
How can All types of radioactive decay be detected?
by photographic film, or a Geiger-Muller tube (G-M tube).
75
What is a photographic film?
The photographic film is chemically changed by the radiations so it can be developed to see if there has been exposure
76
What happens in a Geiger-muller tube?
a G-M tube, the radiations ionise the gas inside and the resulting charged particles move across the chamber and get counted as charges
77
What will a block of radioactive material contain?
will contain many trillions of
nuclei
78
What are not all nuclei likely to do at the same time? And what does this mean?
Decay- so it is impossible to tell when a particular nucleus will decay.
79
What is it not possible to measure in terms of radioactive decay?
which particular nucleus will decay next but given that there are so many of them
80
What is it possible to measure in terms of radioactive decay?
it is possible to say that a certain number will decay in a certain time
81
Scientists cannot tell when a particular nucleus will decay but what they can use?
statistical methods to tell when half the unstable nuclei in a sample will have decayed
82
What is a half-life?
The time it takes for the number of nuclei of a radioactive isotope in a sample to halve
83
What can a half-life also be defined as?
Also defined as the time it takes for the count rate from a sample containing a radioactive isotope to fall to half its starting level.
84
What is the Geiger-muller tube?
The Geiger-Muller tube is a device that detects radiation. It gives an electrical signal each time radiation is detected
85
What are the Geiger-muller signals converted into?
These signals can be converted into clicking sounds, giving a
count rate
in clicks per second or per minute.
86
What is the count rate?
Measure of the amount of radiation reaching a detector in a given time, usually shown as counts per second or counts per minute.
87
How is the activity of a radioactive substance measured?
It is measured in Becquerel (Bq).
88
What is the activity of a radioactive substance?
The number of decays of a radioactive element per second. Measured in Becquerels (Bq).
89
What is one Becquerel is equal to?
One nuclear decay per second
90
Shining visible
radiation
from a torch beam onto a hand lights the hand up why does this happen?
It happens because the hand has been exposed to light.
91
What is irradiation?
Process of exposing an object to a source of radiation
92
What does irradiation apply to?
all types of radiation including radiation from the
nuclei
of
atoms
.
93
Is Irradiation from
radioactive decay
Harmful?
Yes, it can damage living cells. This can be put to good use as well as being a hazard.
94
How can Irradiation can be used to preserve fruit sold in supermarkets?
By exposing the fruit to a
radioactive
source - typically cobalt-60.
95
What Happens once the fruit has been exposed to a radioactive source?
The
gamma rays
emitted by the cobalt will destroy any bacteria on the fruit but will not change the fruit in any significant way.
96
Does irradiation cause fruit to become radioactive?
No
97
When does contamination occur?
Contamination occurs if an object has a
radioactive
material introduced into it.
98
What is contamination?
A substance is contaminated if another substance is mixed or dispersed within it.
99
When does irradiation occur?
It Occurs when an object is exposed to a source of radiation outside the object
100
When does contamination occur?
It Occurs if the radioactive source is on or in the object
101
Does irrigation cause an object to be radioactive?
It Doesn’t cause the object to become radioactive
102
Does contamination cause an object to be radioactive?
A contaminated object will be radioactive for as long as the source is on or in it
103
Can irradiation be blocked?
It Can be blocked with suitable shielding
104
Can contamination be blocked?
Once an object is contaminated, the radiation cannot be blocked
105
Does irradiation stop?
It Stops as soon as the source is removed
106
Does contamination stop?
It can be very difficult to remove all of the contamination
107
Nuclear radiation
can
ionise
chemicals within a body, which changes what?
the way the cells behave.
108
What can nuclear radiation also do as well as change the way the cell behave?
can also deposit large amounts of energy into the body, which can mutate DNA and damage or destroy cells completely
109
What effect does radiation have on the eyes?
High doses can cause cataracts
110
What effect does radiation have on the thyroid ?
Radioactive iodine can build up and cause cancer
111
What effect does radiation have on the lungs?
Breathing in radioisotopes can damage DNA
112
What effect does radiation have on the reproductive organs?
High doses can cause sterility or mutations
113
What effects does radiation have on the skin?
Radiation can burn skin or cause cancer
114
What effects does radiation have on bone marrow?
Radiation can cause leukaemia and other diseases of the blood
115
What does risk of radiation depend on?
The risk associated with radioactive materials depends on the amount of exposure.
116
What increases the risk of harm from radiation?
Being exposed to highly radioactive materials or being exposed to radioactive materials for long periods of time or on a regular basis, increases the dose received
117
What is risk?
Risk is the likelihood of cell damage occurring
118
What are the 7 precautions can be taking to reduce the risk of radioactive sources?
1.keep radioactive sources like technetium-99 shielded (preferably in a lead-lined box) when not in use
2.wear protective clothing to prevent the body becoming contaminated should radioactive isotopes leak out
3.avoid contact with bare skin and not attempt to taste the sources
4.wear face masks to avoid breathing in materials
5.limit exposure time - so less time is spent around radioactive materials
6.handle radioactive materials with tongs in order to keep a safer distance from sources
7.monitor exposure using detector badges, etc
119
Name the man made sources that create background radiation..
2. Buildings and the ground
5. Artificial man made sources (12%)
6. Medical
8. Nuclear power and weapon testing
7. Other sources
9. Artificial sources
120
Name the natural sources that create background radiation..
1. Radon gas from the ground
3. Cosmic rays
4. Food and drink
6. Medical
7. Other sources
121
What does The actual amount of
radiation
that a person is exposed depend on?
where they live, what job they do and many other things.
122
Scientists must always take into consideration the amount of background radiation. Why?
when working or experimenting with radioactive sources and discount it from their results.
123
How does background radiation mainly affect everyone?
By irradiation but a small amount is from being
contaminated
by
radioisotopes
in the food and drink that is consumed.
124
A source that emits one particle per second has an activity of one Bq. However, this particle could be?
this particle could be
alpha
or
beta
and would, therefore, have a different effect on a person’s body.
125
How could a beta particle cause a lot of damage?
a beta particle has a lot of energy but may not cause a lot of damage because of its low
ionisation
power
126
How will an alpha particle cause damage?
an alpha particle will have less energy but will cause more damage in a shorter distance because it is bigger
