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Physics 21st Century > Radioactive materials > Flashcards

Radioactive materials Flashcards

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1
Q

What is the smallest part of an element?

A

The atom

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2
Q

What forms the nucleus of an atom?

A

Neutrons and protons

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3
Q

What is the smallest particle in the atom?

A

The electron.

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4
Q

What is the charge of an electron?

A

-1

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5
Q

What is the relative mass of a proton?

A

1 (Also about 2000 times the mass of an electron)

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6
Q

What is the relative mass of a neutron?

A

1

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7
Q

What is the charge on a neutron?

A

0

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8
Q

What is the charge of an atom?

A

0

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9
Q

What does an atom have that makes it neutral overall?

A

Equal numbers of protons and electrons.

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10
Q

How was evidence on the structure of an atom obtained, by Rutherford and others?

A

They scattered alpha particles using gold foil.

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11
Q

What was the result of the Rutherford-Geiger-Marsden alpha scattering experiment?

A

Most alpha particles went straight through; a few were deflected at small angles; even fewer bounced back.

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12
Q

What was deduced about the structure of the atom using the results of the Rutherford-Geiger-Marsden alpha scattering experiment?

A

The atom must be mostly empty space as most particles went straight through; the mass and charge of the atom is concentrated in a small area (the nucleus); the nucleus is positive as the positive alpha particles were repelled

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13
Q

What hold protons and neutrons together?

A

The strong nuclear force.

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14
Q

What does the strong nuclear force have to balance?

A

The electrostatic repulsion between protons.

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15
Q

What determines which element an atom is, and therefore the chemical properties?

A

The number of protons.

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16
Q

What are isotopes?

A

Atoms of the same element with the same number of protons but different numbers of neutrons. For instance, hydrogen can have 0, 1 or 2 neutrons, to give hydrogen, deuterium and tritium. Most isotopes don’t have different names, you just use the atomic mass!

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17
Q

What is the name for an atom that is unstable?

A

It is radioactive.

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18
Q

What happens when a radioactive element emits ionising radiation?

A

It becomes more stable.

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19
Q

What is the low level ionising radiation that is all around us?

A

Background radiation.

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20
Q

Where does background ionising radiation come from?

A

Some from space, most from rocks and soil.

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21
Q

How can you tell when an individual atom will decay?

A

You can’t, it is random

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22
Q

What determines the amount of energy emitted by a radioactive element?

A

Only the amount of the element, it is unaffected by anything else.

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23
Q

What are the types of ionising radiation (including particle radiation)?

A

Alpha, beta, gamma

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24
Q

What is the charge on an alpha particle?

A

2+

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25
Q

What is the charge on a beta particle?

A

1-

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26
Q

What is the charge on gamma radiation?

A

Neutral

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27
Q

What is the relative mass of an alpha particle?

A

4 (2 protons + 2 neutrons)

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28
Q

What is the relative mass of a beta particle?

A

Almost zero

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29
Q

What is the relative mass of gamma rays?

A

Zero.

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30
Q

Which of the ionising radiations are deflected by magnetic fields?

A

Alpha, beta

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31
Q

Put the radiation types in order of penetration, lowest first.

A

Alpha, beta, gamma

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32
Q

What happens to ionising radiation as it goes through air?

A

It ionises the air molecules and loses energy

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33
Q

How far can alpha particles travel in air? Why?

A

Only a few cm, they are very large and can easily knock off electrons, losing energy.

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34
Q

How far can beta particles travel in air?

A

About a metre

35
Q

What happens to gamma rays in air?

A

They are not stopped by air, but the beam spreads and becomes less intense.

36
Q

What is an alpha particle?

A

A helium nucleus.

37
Q

What is a beta particle?

A

An electron

38
Q

What are gamma rays?

A

The highest frequency type of electromagnetic radiation.

39
Q

What can ionising radiation do to living cells?

A

It can damage them.

40
Q

What damage is done to living cells by radiation?

A

It depends on the type of radiation, and the intensity.

41
Q

What happens inside the cell when ionising radiation hits?

A

Electrons are knocked out of atoms, leaving positive ions, which then react with other chemicals in the cell.

42
Q

What can happen to a cell with high intensity radiation?

A

It can stop the cell’s ability to divide, making it sterile.

43
Q

What can happen to a cell with lower intensity radiation?

A

The DNA molecule can be damaged, a mutation.

44
Q

What stops alpha particles from entering the body?

A

The skin, the outside of which is dead cells.

45
Q

Why are beta and gamma from dangerous than alpha to living organisms?

A

They are able to get inside the body, where they can cause harm.

46
Q

How is the biological effect of radiation measured?

A

The Sievert, it measures alpha, beta and gamma.

47
Q

Which atoms in the body are highly susceptible to ionisation?

A

Oxygen, hydrogen, carbon, nitrogen

48
Q

What happens to the number of protons and neutrons when an alpha particle is emitted?

A

2 neutrons, and 2 protons are lost. The relative atomic mass goes down by 4, and the proton (atomic) number by 2.

49
Q

What happens to the number of protons and neutrons when a beta particle is emitted?

A

1 neutron turns into a proton, so the atomic number goes up by one, and the relative atomic mass stays the same..

50
Q

What happens to the number of protons and neutrons when an gamma ray is emitted?

A

Nothing

51
Q

What state is an unstable nucleus in?

A

An energetic state, it effectively has a form of potential energy.

52
Q

What is the half-life of an element?

A

The time taken for half the atoms to decay.

53
Q

How long is a half-life?

A

It varies with the element. Some man made elements have half-lives of fractions of seconds. (We think of them as man made… but actually, how would we find them if a nova did make them?)

54
Q

What proportion of a radioactive sample would you find after 3 half lives?

A

1/2 x 1/2 x 1/2

55
Q

What are the uses of ionising radiation?

A

Treating cancer; sterilising medical instruments; sterilising food; detecting tumours;

56
Q

How is ionising radiation used to treat cancer?

A

Gamma radiation is used to kill cancer cells. It can damage other tissues too.

57
Q

How is ionising radiation used to sterilise instruments?

A

Gamma radiation is used to kill bacteria.

58
Q

How is ionising radiation used to sterilise food?

A

Gamma radiation is used as it can get through packaging and kill all micro-organisms.

59
Q

How is ionising radiation used to find cancer?

A

A radioactive tracer is injected. The tumour usually has a faster metabolism than the surrounding tissue, so takes up more, which will show up on the scan. Beta or gamma emitters are used as the radiation needs to come out of the body. The half life needs to be long enough to allow the tracer to be taken up by the tissue, but not so long that it damages the patient.

60
Q

What is exposure to radiation called?

A

Irradiation.

61
Q

When are we exposed to radiation?

A

All the time.

62
Q

How can the risk of radiation be evaluated?

A

The dose equivalent in Sieverts can be calculated which gives and indication of the level of risk, and what harm may have been done.

63
Q

What is it called when you come into contact with radioactive material?

A

Contamination.

64
Q

How do we minimise the risk of contamination from radioactive waste?

A

Waste is either contained, or diluted.

65
Q

How are radiographers protected against radiation?

A

Lead shielding, either an apron or walls.

66
Q

How can radiation be monitored for someone in a risky job?

A

A film badge can monitor radiation,it will become dark as it is exposed to radiation.

67
Q

What could be done after a nuclear explosion to reduce the risks of contamination?

A

Administration of iodine to the population would help, as radioactive iodine is a major product of uranium fission..

68
Q

What is the release of energy by a heavy nucleus splitting in two?

A

Nuclear fission

69
Q

What is the release of energy by two light nuclei combining?

A

Nuclear fusion.

70
Q

Materials that can provide energy by changes in the nucleus are called?

A

Nuclear fuels.

71
Q

Why do nuclear fusion/fission release so much more energy than chemical reactions?

A

The energy that hold nuclei together (binding energy) is much greater than the energy that holds electrons in place.

72
Q

How does nuclear fission work?

A

A neutron is fired at a heavy nucleus (plutonium, uranium), which makes the nucleus split, and gives off more neutrons to split other nuclei.

73
Q

What is meant by critical mass?

A

The amount of fuel needed to make the chain reaction start (as there is so much space between nuclei you need at least one neutron from every reaction to hit to form a chain reaction).

74
Q

What is the equation for energy released?

A

E = mc^2 (m is the mass lost, c is the velocity of light, so 3 x 10^8 m/s)

75
Q

How much of the UK’s power comes from nuclear power stations?

A

About 1/6th

76
Q

What process do our nuclear power stations use?

A

Nuclear fission

77
Q

What does nuclear fission produce?

A

Radioactive waste.

78
Q

How are nuclear wastes categorized?

A

Low level, intermediate level, high level

79
Q

What would be low level nuclear waste?

A

Clothing, paper - it is burned and sealed in containers before going in to landfill.

80
Q

What would be medium level nuclear waste?

A

Chemical sludge, or reactor parts - needs shielding, may well be buried deep underground.

81
Q

What would be high level nuclear waste?

A

The fuel rods - sometimes mixed with molten glass, then sealed in drums.

82
Q

What do the fuel rods contain as fuel?

A

Pellets of uranium.

83
Q

How is the energy of the nuclear reaction converted?

A

Radioactivity produces heat, which is passed to the coolant, passed on to water that is brought to the boil and the steam turns turbines.

84
Q

How is the nuclear reaction controlled?

A

Control road (often made of boron) are lowered to absorb neutrons to slow the reaction, or raised to allow more neutrons to initiate chain reactions.

Physics 21st Century (8 decks)

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