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Physics > Topic 3 - Radioactivity > Flashcards

Topic 3 - Radioactivity Flashcards

1
Q

How did Democritus describe atoms?

A

He described them as small spheres that are the smallest possible unit of matter that are separated from each other by empty space

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2
Q

How did Dalton describe atoms and what did he suggest about elements?

A

He described them as solid spheres and suggested that the different types made up the different elements

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3
Q

What is the plum pudding model and who made it?

A

The idea that the atom is a ball of positive charge with electrons dotted throughout, it was created by J.J Thompson

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4
Q

What did Rutherford do?

A

He fired alpha particles at thin sheets of gold foil and some where deflected in different direction instead of passing through; he hypothesised that there was a dense region of positive charge at the centre of the atom that repelled the alpha particles, from this he created the Nuclear model

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5
Q

What does the nuclear model say/

A

It says that in atoms there is a central positive nucleus which is surrounded by electrons

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6
Q

What was the issue with Rutherford’s nuclear model?

A

Bohr stated that the nuclear model could not work as the electrons would be attracted to the nucleus, causing the atom to collapse; he hypothesised that electrons orbit the nucleus in shells

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7
Q

What particles are found in the nucleus of an atom?

A

Protons and neutrons

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8
Q

What charge do protons, neutrons and electrons have?

A

Protons: +1
Neutrons: 0
Electrons: -1

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9
Q

What are the relative masses of protons, neutrons and electrons?

A

Protons: 1
Neutrons: 1
Electrons: 0.0005

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10
Q

What is the mass number of an element?

A

The number of protons + the number of neutrons

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11
Q

What is the atomic number of an element?

A

The number of protons

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12
Q

Which is the top number of an element as shown in the periodic table?

A

The mass number

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13
Q

What is an isotope?

A

Isotopes are atoms with the same number of protons but a different number of neutrons

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14
Q

What can happen if an isotope is unstable?

A

They can decay into other elements, which involves emitting alpha, beta or gamma radiation

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15
Q

What is excitation?

A

When the electrons absorb electromagnetic radiation and jump to a higher shell (further from the nucleus).

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16
Q

What is de-excitation?

A

When excited electrons emit their electromagnetic energy and fall back down to their original position

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17
Q

What is ionisation?

A

When the electrons gain enough electromagnetic energy to leave the atom altogether

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18
Q

Why can radioactive materials decay?

A

They contain unstable isotopes

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19
Q

What does an alpha particle consist of?

A

2 neutrons and 2 protons

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20
Q

How can we describe an alpha particle?

A

It is the same as a helium nucleus, it has no electrons and a charge of +2

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21
Q

What does a beta particle consist of?

A

1 electron

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22
Q

What does gamma radiation consist of?

A

Electromagnetic radiation

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23
Q

What are the charges of alpha, beta and gamma radiation?

A

Alpha: 2+
Beta: 1-
Gamma: no charge

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24
Q

What causes the emission of a neutron?

A

A nucleus having too many, causing it to be an unstable isotope

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25
Order the 3 types of radiation from most to least penetrative
Gamma: Can penetrate aluminium but not thick lead Beta: Can penetrate paper but not 5mm of aluminium Alpha: Cannot penetrate paper
26
What is the source of a beta particle?
A neutron decaying into a proton and electron
27
How can we describe a beta particle?
it is the same as an electron, it has no protons or neutron and has a charge of -1
28
Order the 3 types of radiation from most to least ionising
Alpha: Strongly ionising Beta: Moderately ionising Gamma: Weakly ionising
29
In the equation 232 (mass no.) 90 (proton no.) Th --> a b Ra + 4 2 He, what do a and b represent?
A = 228 B = 88
30
What do you need to make sure with nuclear decay equations?
That the sum of the mass numbers and the sum of the atomic numbers of both sides are equal
31
What are the symbols for the 3 types of radiation?
Alpha: a Beta: β Gamma: y
32
For a single atom does the decay process occur at regular intervals?
No it is random
33
What is the activity of decay?
It is the overall rate of decay of all the radioactive isotopes in the sample
34
How do we measure radioactive activity?
Becquerels (Bq) - the number of decays per second
35
What is half-life for a radioactive sample?
The time taken for the activity to halve and for the number of radioactive nuclei in the sample to half
36
Does a sample's half-life decrease over time?
No, a sample's half-life remains constant
37
How do you record radioactive decays?
Using a Geiger-Muller tube and counter
37
What is irradiation?
The process by which objects are exposed to radiation
38
What type of radiation are alpha, beta, gamma radiation and X-rays?
Ionising radiation
39
What is contamination?
When radioactive particles get into your body or other objects
40
What is the main difference between contamination and irradiation?
Contamination makes the object radioactive whereas irradiation does not
41
What factors determine how harmful radiation can be to a person?
The amount of radiation received, where you are exposed to it and the type of radiation
42
What 3 things could happen if DNA is exposed to radiation?
The DNA could mutate, be destroyed or divide uncontrollably and become cancerous
43
List the types of radiation from least to most harmful
Radiowaves, microwaves, infrared, visible light, ultraviolet. X-rays, gamma, beta and alpha
44
Which radioactive substance would be the most harmful in the body?
Alpha because it is the most ionising
45
What safety precautions should you take when handling radioactive substances?
Wear overalls, use tongs to pick it up and store in a lead-lined box
46
What happens to cells that receive a large dosage of radiation?
They die
47
List 3 common symptoms of radiation poisoning
Vomiting, tiredness and hair loss
48
How can radiation cause cancer?
The radiation can cause DNA mutations which can cause the cells to divide uncontrollably and become cancerous
49
What is radiotherapy?
The use of targeted doses of radiation to kill cancer cells
50
What is external radiotherapy?
The body is exposed to gamma rays (because they are the most penetrative) from outside of the body, from lots of different angles. This way only the cancer site gets the most radiation
51
What is internal radiotherapy?
The body is exposed to radiation from inside of the body. The radiation source usually emits beta particles and is placed inside or near cancer cells
52
What are 2 side effects of radiotherapy?
The patient feels sick and the treatment also kills healthy cells
53
How do tracers work
A tracer (radioactive isotope) is injected or swallowed by a person. If injected, it will travel to parts of the body via bloodstream and if swallowed it will be absorbed in the intestine and then travel vie the bloodstream. The radiation the tracer emits allows us to see the movement and accumulation of it.
54
what is important for tracers?
They need to have a short half-life so that the time the patient is exposed to radiation is minimal and it needs to be gamma as it is the most penetrative (easy to detect) and least ionising (less harm)
55
What does the PET in PET scans stand for?
Positron Emission Topography
56
How do PET scans work?
Tracers are injected into the bloodstream that spread through the body and emit gamma radiation, by seeing where the radiation is emitted the doctors can see where the tracers are and diagnose medical issues
57
what is important about PET scan tracers?
They must be made near to the hospital as they need a short half-life to minimise the radiation exposure for the patient
58
What is nuclear fission?
The splitting up of a large and unstable nucleus into smaller nuclei
59
What is spontaneous fission and is it common?
Spontaneous fission is where the fission is unforced and the atom splits by itself - it is rare
60
How can fission occur?
The nucleus can absorb a neutron and become even more unstable. The neutron helps to split the nucleus
61
How does a nuclear fission chain reaction occur?
The neutron is fired at the unstable nucleus, causing it to split apart into to daughter nuclei and 2-3 other neutrons while also emitting lots of energy in the form of gamma radiation. The 2-3 other neutrons are absorbed by other unstable nuclei and the process repeats in a chain reaction
62
How do nuclear power stations generate electricity?
The gamma radiation released by the splitting of the unstable nuclei turns liquid water into steam and as it rises it turns turbines and the kinetic energy of the turbines is converted to electricity by a generator
63
How do we ensure safety in nuclear reactors?
Control rods can be lowered that absorb neutrons and slow down the chain reaction
64
What are 3 positives of nuclear power?
Doesn't produce greenhouse gas, radioactive fuel (uranium/plutonium) is relatively cheap and it can produce a large and steady electric power
65
What are 3 negatives of nuclear power?
Power stations are very expensive to build, radioactive waste is very expensive to store and there is a risk of nuclear meltdown
66
What is nuclear fusion
the fusing of 2 lighter nuclei to create a single heavier nucleus. When this occurs, a lot of energy is emitted in the form of electromagnetic radiation
67
Where does the energy released in nuclear fusion come from?
Some of the mass is converted into energy
68
Where does nuclear fusion commonly occur?
In stars; it is why they have so much energy
69
What is happening in the nuclear fusion of stars?
Hydrogen nuclei are fusing into helium nuclei
70
Why does fusion only occur at very high pressures and temperatures?
To overcome the forces of repulsion of the 2 nuclei
71
In the alpha particle scattering experiment, most of the alpha particles passed straight through the gold sheet, what does this suggest?
It suggests that the atom is mostly empty space
72
in the alpha particle scattering experiment, some positively charged alpha particles were deflected through large angles, what does this suggest?
The deflections through the large angles suggests that the nucleus repels that alpha particles. This means it is positive because like charges repel. It also means that most of the mass of an atom is concentrated in the centre
73
How would you draw a diagram of the alpha particle scattering experiment with a setup like this: a a a Au a a
The top and bottom lines wouldn't be deflected so would just be a straight line, the 2nd and 4th from the top would be deflected away below 90 degrees and the middle line would be deflected greater than 90 degrees
74
Explain what led to the replacement of the plum pudding model
The alpha particle scattering experiment, where alpha particles were fired at a sheet of gold foil, led to its replacement. Most of the particles passed straight through, suggesting most of the atom is empty space, a few alpha particles were deflected at large angles, so most of the mass is concentrated at the centre of the atom and the nucleus is positively charged because like charges repel

Physics (4 decks)

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