GCSE Physics 🪐 > Radioactivity 📄 > Flashcards

Radioactivity 📄 Flashcards

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1
Q

What is the structure of the atom?

A

Positively charged nucleus consisting of protons and neutrons.
Surrounded by negatively charged electrons which orbit the nucleus in shells

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2
Q

What is the mass and charge of an electron?

A

1/1340
-1

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3
Q

What is the mass and charge of a proton?

A

1
+1

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4
Q

What is the mass and charge of a neutron?

A

1
0

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5
Q

Where is most of the mass of an atom found?

A

In the nucleus

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6
Q

What is an isotope?

A

An atom of an element with the same number of protons but a different number of neutrons.
This results in the same atomic number but a different atomic mass.

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7
Q

What happens in excitation?

A

Electrons move to a higher orbit by absorbing em radiation

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8
Q

What happens in de-excitation?

A

Electrons move to a lower orbit as the atom has emitted em radiation

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9
Q

What happens if an electron gains enough energy?

A

It can leave the atom to form an ion

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10
Q

What are the 4 types of radioactive decay?

A

Alpha
Beta +
Beta -
Gamma

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11
Q

What type of process is radioactive decay?

A

Random

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12
Q

What is alpha decay?

A

A helium nucleus
2 protons, 2 neutrons

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13
Q

What is beta - decay?

A

Electron

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14
Q

What is beta + decay?

A

Positron

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15
Q

What is gamma decay?

A

Photon of em radiation, gamma ray

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16
Q

What are the characteristics of alpha decay?

A

Highly ionising and lowly penetrating

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17
Q

What are the characteristics of beta - decay?

A

Medium ionising
Medium penetration

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18
Q

What are the characteristics of beta + decay?

A

Medium ionising
Medium penetration

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19
Q

What are the characteristics of gamma decay?

A

Lowly ionising
Highly penetration

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20
Q

What is background radiation?

A

Weak radiation that can be detected from natural/external sources

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21
Q

What are some examples of background radiation?

A

Cosmic rays
Radiation from underground rocks
Nuclear fallout
Medical rays

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22
Q

How do we measure radioactivity? (2 methods)

A
  1. Photographic film (film goes darker when it absorbs radiation, worn as badges by people who work with radiation to check exposure)
  2. Geiger Muller Tube
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23
Q

What is a Geiger muller tube?

A

A tube which can detect radiation

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24
Q

How does a Geiger muller tube work?

A

Each time it absorbs radiation, it transmits an electrical pulse to the machine, which produces a clicking sound

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25
What did JJ Thompson discover about the atom in 1897?
The electron.
26
What model did JJ Thompson produce?
The Plum Pudding Model
27
What is the plum pudding model?
Sphere of positive charge dispersed with negative electrons throughout. Overall charge of 0
28
What did Rutherford discover in 1911?
The atom was mostly empty space
29
Describe the outcomes of the gold foil experiment:
Most particles went straight through - so mostly empty space Some alpha particles were slightly deflected - nucleus must be positive repelling positive alpha Few (1 in 8000) were deflected by >90* - nucleus contained most of the mass
30
Who carried out the gold foil experiment?
Geiger and Marsden
31
What was Rutherford’s model of the atom?
Positive nucleus in centre of the atom and negative electrons exist in a cloud around the nucleus
32
What did Bohr discover in 1913 about the atom?
If Rutherford was right then the electrons in the cloud close to the nucleus would get attracted and cause the atom to collapse. **Therefore, the electrons must exist in fixed orbitals.**
33
Order of Atomic Structure discoveries:
1. 1800 Dalton said everything was made of atoms 2. 1897 JJ Thompson discovered the electron (Plum Pudding Model) 3. 1911 Rutherford’s Gold Foil Experiment 4. 1913 Bohr’s Model
34
What happens in beta - decay?
Neutron becomes a proton and releases an electron
35
What happens in beta + decay?
Proton becomes a neutron and releases a positron
36
How does alpha decay change the original nucleus?
- 4 mass number - 2 proton number
37
How does beta decay change the original nucleus?
+1 proton number
38
How does gamma decay change the original nucleus?
It doesn’t. Photon of gamma radiation has no charge
39
What is activity?
Number of decays in a sample per second
40
What happens to activity overtime?
Decreases exponentially
41
How is activity measured?
Becquerel, Bq
42
What is the half life of an isotope?
Time taken for half the nuclei in a sample to decay
43
Uses of radioactivity and types: Gamma
Sterilising equipment Irradiating food Diagnosis and treatment of cancer
44
Uses of radioactivity and types: Beta
Tracing and gauging thickness
45
Uses of radioactivity and types: Alpha
Smoke alarms
46
Is having a short half life dangerous?
It present less risk as it doesn’t remain strongly radioactive for a long time. Initially it’s very radioactive but quickly dies down So LESS LONG TERM RISK
47
Is having a long half life dangerous?
Yes, it remains weakly radioactive for a long period of time. So longer exposure presents more of a risk
48
What are some safety measures against radioactivity?
- Limiting patient dose - short Half life - Limiting risks to medical personnel includes leaving the room during radioactive tests, as their everyday close proximity to the sources puts their health at risk in the long term. - wearing ppe
49
What is contamination?
The source of radiation is transferred to an object
50
What is irradiation?
The sources emits radiation which reaches an object
51
How long does irradiation last for?
Short period
52
How long does contamination last for?
Long period
53
Describe the external treatment of tumours:
A beam of gamma radiation rotates around the body continually focused on the tumour to ensure minimal damage to healthy cells while tumour is most affected Takes a long time and multiple visits Greater risk of long term side effects
54
Describe internal treatment of tumours:
Radioactive material is held within a needle and injected directly into the tumour Requires a long period of time in hospital as some implants have high radioactivity (you emit radiation)
55
What is a PET?
Positron Emission Tomography
56
What does a PET scanner do?
Inserts a radioactive tracer into the body, tagged to the desired chemical and the traced therefore travels in the body where this certain chemical travels. Scanned the. Records where the tracer emits radiation and produces a live 3D visualisation of the body.
57
Why is the isotope in PET scanners made locally just before insertion?
Because it has a short half life so cannot be stored for long before it decays
58
What is nuclear fusion?
Process of small nuclei being forced righted under immense temperatures and pressure to form a heavier nucleus
59
What is nuclear fusion the energy source for?
Stars
60
Why is a lot of energy required in nuclear fusion?
Electrostatic repulsion of the protons in 2 different nuclei means a lot of energy is required to bring the nuclei close enough to fuse
61
Have we achieved practicable nuclear fusion?
No, temps and pressures are too high
62
Does nuclear fusion or fission produce radioactive waste?
Fission
63
What is nuclear fission?
Process of a nucleus splitting into 2 smaller nuclei after absorbing neutrons, which releases more neutrons creating a chain reaction.
64
The products of fission are …
Radioactive
65
What is a chain reaction (link in nuclear fission)?
After one nucleus splits, emitting burgeons, these neutrons cause further fission which releases more neurons in a continuous process
66
What do moderators do in a nuclear fission reactor?
Usually water or graphite Slows down emitted neutrons to be absorbed for further fissions as fast moving neutrons cannot be easily absorbed
67
What do control rods do in a nuclear fission reactor?
Boron rods in reactor core which absorb excess neutrons preventing a runaway chain reaction
68
How does a nuclear fission reactor work?
Heat energy from chain reaction is absorbed by water (coolant) which evaporates into steam and is used to turn a turbine, which turns a generator which generates electricity
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