Radioactivity Flashcards
1
Q
What is an atom
A
A positively charged nucleus surrounded by negatively charged electrons
2
Q
What is the size of atom
A
0.1 nanometres (10^-10)
3
Q
What is the relative mass and charge of a proton
A
Relative Mass: 1
Relative Charge: +1
4
Q
What is the relative mass and charge of a neutron
A
Relative Mass: 1
Relative Charge: 0
5
Q
What is the relative mass and charge of a electron
A
Relative Mass: 0.0005
Relative Charge: -1
6
Q
What is the relative mass and charge of a positron
A
Relative Mass: 0.0005
Relative Charge: +1
7
Q
What is an isotope
A
An element with same amount of protons but different amount of neutrons
8
Q
What is the mass number of an atom
A
no* neutrons + protons
9
Q
What happens when an electron moves to a high orbit (away from the nucleus)
A
The atom has absorbed EM radiation
10
Q
How does an electron become an ion
A
When it gains enough energy to leave the atom
11
Q
What does it mean for an electron to be excited
A
It has absorbed EM radiation
12
Q
What happens to an excited electron in an atom
A
It moves to a high orbit (moving away from the nucleus and onto a further shell)
13
Q
What happens when an electron loses energy
A
electron falls to a low orbit (closer to the nucleus)
14
Q
What are the 4 main forms of decay
A
- Alpha
- Beta
- Gamma
- Neutron
15
Q
How is radioactive decay emitted
A
By an unstable nuclei
16
Q
Why are most isotopes unstable
A
1- Big in size
2- Excess/ limited amount of neutrons
17
Q
Describe the properties of an alpha particle (α)
(3 points)
A
- Same as a helium nucleus
- 2 protons, 2 neutrons
- 2+ charge
18
Q
Describe the ionising and penetrating levels of an alpha particle
A
- Highly ionising
- Weakly penetrating
19
Q
What is a beta minus β- particle
A
Fast-moving electrons emitted from the nucleus
20
Q
What is a Beta plus particle
A
Fast moving positrons produced when a neutron changes into an electron and proton
21
Q
Describe the ionising and penetrating levels of a Beta particle
A
- Moderately ionising
- Moderately penetrating
22
Q
Charge of a beta minus particle and beta plus particle
A
Beta minus = -1
Beta plus = +1
23
Q
Describe the properties of gamma rays γ
A
- Electromagnetic waves
- No charge or mass
24
Q
Describe the ionising and penetrating levels of Gamma rays
A
- Low ionising
- Highly penetrating
25
What material is able to stop Alpha radiation
Paper or the outer layers of skin
26
What material can absorb Beta radiation
a few mm of Aluminium
27
What material can absorb gamma rays
1. metres of concrete
2. several centimetres of lead
28
What is background radiation
radiation that exists around us all the time
29
What are 3 natural sources of background radiation
1. Radon gas from rocks and soil
2. Cosmic rays from space
3. Radioactive material in foods (i.e bananas)
30
What are 3 man-made sources of background radiation
1. Medical sources
2. Nuclear fallout after a nuclear explosion
3. Nuclear accidents such as Chernobyl
31
How can photographic film be used to measure background radiation
Film is initially white and turns black as more radiation is absorbed
32
How does a Geiger-Muller tube measure radiation
1. As it absorbs radiation, it transmits an electrical pulse to the tube
2. Tube produces a clicking sound.
3. Higher the frequency of clicks, the more radiation present.
33
Describe the process of β– decay
1. emitted by nuclei with too many neutrons
2. neutron changes into a proton and an electron
3. electron is emitted & proton remains in nucleus
34
How does beta minus decay affect the element
Atomic number increases by +1
35
Describe the process of β+ decay
1. Emitted by nuclei with excessive protons
2. Proton turns into a neutron emitting a positron
3. Positron = emitted
Neutron = remains in nucleus
36
How does Beta+ decay affect a nuclei
Atomic number decreases by -1
37
What is the nuclear transformation for alpha emission
1. The atomic (proton) number decreases by 2
2. The mass (nucleon) number decreases by 4
38
What is the nuclear transformation for gamma radiation
No protons or neutrons are lost and therefore nothing changes
39
Describe neutron emission
1. The atomic (proton) number does not change
2. The mass (nucleon) number decreases by 1
40
What usually happens after the radioactive decay of a nuclei
often have excess energy which is released as gamma when atom rearranges
41
Define activity within radiation decay
The rate at which the unstable nuclei from a source of radiation decays
42
What is the unit for activity and what does it equate to
Becquerels (Bq) = 1 nucleus in the source decaying in 1 second
43
What is half-life
The time taken for half the undecayed nuclei to decay or the activity of a source to decay by half
44
Can half-life be predicted?
No; however the rate that the activity decreases can be predicted
45
How do you work out net decline
initial number - number after X half-lives / initial number
46
How do you measure the half-life of a sample
1. Measure the initial activity, A0, of the sample
2. Determine the half-life of this original activity
3. Measure how the activity changes with time
47
How is radiation used in radiotherapy
Gamma rays are used onto the tumour killing it's DNA therefore slowing/killing cancerous cells
48
How is radiation used in tracers
Gamma/Beta is injected into the body and using an external detector it's progress is followed around the body - tests to see if organs are absorbing the right amount and if not flags up cause for concern
49
Why isn't Alpha radiation used in tracers
As it can only pass through a thin sheet of paper so the radiation would not be able to pass through the body into the surroundings
50
How is radiation used in thickness gauges for materials such as foil/paper
Radiation is absorbed when passing through materials
1- If a material is too thick - more beta particles are absorbed and less are picked up by the tracer sending a signal to the rollers to increase the force on the material, making it thinner.
2- If material is too thin - less beta particles are absorbed and more are picked up by the tracer sending a signal to reduce the force on the material making it thicker
51
How is radiation used in smoke alarms
Americium-241 is found in smoke alarms (alpha emitter)
Alpha particles ionise air particles making them charged and forms a current
Smoke entering the detector will be absorbed which stops the current and triggers the alarm
52
How is radiation used within irradiating food
Gamma rays (colbalt-60) are emitted onto food to destroy any bacteria and increasing shelf life
53
How is radiation used to treat cancerous cells
Beams of gamma ray (a.k.a gamma knife) are aimed at the tumour at different angles to maximise the dose without harming healthy tissue
54
How is radioactive materials used for sterilising material
Irradiating the equipment kills any living organisms, preventing pathogens from being transferred
55
Why are gamma rays the best for irradiating food
It's the most penetrating
56
How can ionising rays cause cancer
Atoms exposed to radiation either die or break within the DNA - wrong reformation could lead to mutations which if replicated can cause cancer
57
How do ionising rays cause tissue damage
High energy rays such as gamma and x-ray can cause the damage of healthy tissue during treatments
58
What are 2 safety measures that can be taken when using radiation in medicine
1- Use radioactive material with a short half-life which can be quickly removed after a day
2- isolate them from the radioactive material as every-day exposure can cause cancer
59
What is contamination (short-lasting or long-lasting?)
Longlasting: The source of radiation is transferred towards an object
60
What is irradiation (short-lasting or long-lasting?)
Shortlasting: A source emits radiation which reaches an object
61
How are tumours treated using internal radiotherapy
Small pellets of radioactive materials are inserted into a tumour
62
How are radioactive substances used in PET scanners
1- Radioactive tracers are tagged to the desired chemical
2- When inserted the tracer travels to where the chemical is usually located
3- The radioactive atom on tracer loses radioactivity producing a positron
4- The positron hits an electron at high speeds they combine and destroy emitting gamma rays in opposite directions
5- PET scan records from the different angles where the racer is and produces a 3D image
63
Why do the isotopes in PET scanners have to be produced nearby
As they contain a half time of 110mins
64
What are 3 advantages of nuclear power stations
1. Doesn't produce carbon dioxide
2. Low fuel cost and quantity
3. Long lifetime
65
What are 2 disadvantages of nuclear power stations
1. Waste is radioactive and difficult to dispose
3. Large-scale accidents are catastrophic
66
What is nuclear fusion
the process of small nuclei being forced together (under immense temperature and pressure) to form a heavier nucleus
67
Why does fusion happen at such high pressures and temperatures
To overcome the electrostatic repulsion
68
What is fission
The splitting up of large and unstable nuclei into smaller nuclei
69
What are the steps of fission of Uranium-235
1- Unstable nucleus of 235 absorbs 2 more neutrons causing it to be less stable
2- As a result it splits apart into daughter nuclei releasing energy in gamma radiation and two more neutrons
70
How does the nuclear reactions including fission and fusion produce energy
Fission - energy for power plants
Fusion - energy source for stars
71
How do moderators control a chain reaction within a nuclear reactor
Graphite or Heavy water material that slows down the neutrons released from fission so that they cause more fission.
72
How do control rods control a chain reaction within a nuclear reactor
Boron rods in the reactor core absorb excess neutrons to prevent a runaway chain reaction
73
How does thermal energy from chain reactions get used to create electricity
Thermal energy from the reaction is absorbed by coolant (water) which then evaporates into steam. The steam is used to turn a turbine which is used to generate electricity.
