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AQA GCSE Physics > Atomic and Nuclear Physics > Flashcards

Atomic and Nuclear Physics Flashcards

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1
Q

Describe the model of the atom:

A

There is a tiny, dense, positively charged nucleus at the centre of ‘empty space’ with an electron cloud

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2
Q

To what order is the diameter of the atom?

A

~10^-10

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3
Q

To what order is the diameter of the nucleus?

A

~10^-15

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4
Q

What is the charge of a proton?

A

+1.6 x 10^-19 C

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5
Q

What is the charge of a neutron?

A

0C

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6
Q

What is the charge of a electron?

A

-1.6 x 10^-19 C

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7
Q

How would an isotope be defined?

A

A form of an element
that has the same number of protons
but a different number of neutrons
compared to the most abundant form.

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8
Q

What is the nucleon number?

A

The number of protons and neutrons in the nucleus of an atom

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9
Q

A radioactive substance contains unstable nuclei. What do unstable nuclei have?

A

An inbalance of energy between the nucleons

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10
Q

How does a particle become more stable?

A

By improving the balance of energy between the nucleons.

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11
Q

How is the balance of energy between the nucleons improved?

A

By emitting energy from the nucleus in the form of:

  • Mass
  • Electromagnetic radiation (carried by photons)
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12
Q

Alpha Decay is a mechanism of radioactive decay, what does it do?

A

Ejects two protons and two neutrons (as a single particle) from the nucleus

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13
Q

What is Beta decay?

A

The emission of an electron from the nucleus- a neutron turns into a proton and emits an electron

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14
Q

What is gamma decay?

A

The emission of high frequency (high energy) electromagnetic radiation from the nucleus

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15
Q

What does ionising ability indicate?

A

How much each radiation type interacts with matter

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16
Q

What is the relative charge of an alpha particle?

A

+2 (two protons)

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17
Q

What is the relative charge of a beta particle?

A

-1 (one electron)

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18
Q

What is the relative charge of a gamma particle?

A

0

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19
Q

What is the relative mass if an alpha particle?

A

7000

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20
Q

What is the relative mass of a beta particle?

A

1

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21
Q

What is the relative mass of a gamma particle?

A

0

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22
Q

What is the range in air for alpha radiation?

A

a few centimetres

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23
Q

What is the range in air for beta radiation?

A

of the order of a metre

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24
Q

What is the range in air for gamma radiation?

A

infinite

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25
Q

What is alpha radiation stopped by?

A
  • Paper

- Skin

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26
Q

What is beta radiation stopped by?

A

a few millimetres of aluminium

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27
Q

What is gamma radiation stopped by?

A

Many centimetres of lead or metres of concrete (sometimes combination)

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28
Q

What is the ionising ability of alpha radiation?

A

Very high

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29
Q

What is the ionising ability of beta radiation?

A

Low (medium)

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30
Q

What is the ionising ability of gamma radiation?

A

Very low

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31
Q

What type of process is radioactive decay?

A

random

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32
Q

What does a Geiger counter detect?

A

Emitted waves or particles from a sample

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33
Q

What does a Geiger counter display to show the radiation?

A

A count rate

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34
Q

What did Rutherford observe happen to alpha particles in his gold leaf experiment in 1911?

A

That some alpha particles went through the thin metal foil but others were scattered by large angles

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35
Q

What was Rutherfords new model?

A

Most the atom is empty space but there is a small, massive, positively charged nucleus in the centre of the atom with electrons orbiting around it

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36
Q

How did Rutherford’s model fit in with his observations made in the experiment?

A

Most of the alpha particles went through the foil, so most the atom is empty space. Some alpha particles were scattered back, so there is a very small, dense, positively charged nucleus at the centre of the atom which repels the positive alpha particles

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37
Q

Compare the changes in the nucleus with alpha and beta decay

A

In alpha decay, the nucleus loses 4 particles, 2 protons and 2 neutrons so the nucleon number decreases by 4. In beta decay, the nucleon number remains the same as the nucleus loses 1 neutron but gains 1 proton

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38
Q

Compare gamma emission and neutron emission

A

In both, an uncharged particle/wave are emitted and the element remains the same. In gamma however, an electromagnetic wave is emitted and the mass of the atom stays the same. In neutron emission, a particle is emitted so the mass decreases.

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39
Q

Define irradiation

A

A process by which a substance is exposed to radiation (and is therefore not the actual source of radiation)

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40
Q

How can we tell if alpha radiation is being emitted by a sample?

A

Set up a Geiger counter so it is detecting radiation from the sample.. Put a sheet of paper between the counter and sample. If the count rate of the counter goes down, the sample is emitting alpha radiation

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41
Q

How can we tell if beta radiation is being emitted by a sample?

A

Set up the same process as for alpha radiation but if the count rate doesn’t go down for a sheet of paper, but does go down for a sheet of aluminium, the sample is emitting beta radiation.

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42
Q

How can we tell if gamma radiation is being emitted by a sample?

A

If the count rate on the Geiger counter remains the same if paper and aluminum have been put between the counter and sample, the sample is emitting gamma radiation.

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43
Q

Timeline of model of atom discovery:

A

1897 - J.J. Thompson discovers electrons
1911 - Ernest rutherford creates nuclear model
1913 - Bohr discovers the energy levels for electrons
1924 - de Broglie establishes wave nature of electrons
1932 - Chadwick discovers the existence of the neutron

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44
Q

What does gamma radiation have a high something of?

A

Penetration ability

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45
Q

What are two hazards associated with handling radioactive materials?

A

Irradiation

Contamination

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46
Q

What is radioactive contamination?

A

Particles of radioactive material left on an object

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47
Q

What kind of process is radioactive decay? Why?

A

Random process as it is impossible to predict which specific nuclei will undergo decay at any particular instant

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48
Q

How can patterns still emerge from the randomness of radioactive decay?

A

Because of the enormous numbers of radioactive nuclei presentin even a small sample

49
Q

What is activity?

A

The number of decays per second

50
Q

What is the activity of a sample dependent on?

A

The number of radioactive nuclei in the sample

51
Q

What is activity measured in?

A

Becquerel, Bq

52
Q

What does 1Bq represent?

A

One decay per second

53
Q

What is the relationship between the activity and number of radioactive nuclei in a sample?

A

Directly proportional

54
Q

Define the half-life of a substance:

A

the time taken for the number of radioactive nuclei in a sample to reduce by half

55
Q

Is half-life independent or dependent of the size of the sample?

A

Independent

56
Q

What is the variation between the half lives of substances?

A

From billions of years to billionths of a second

57
Q

What type of decay (related to maths) is the decay of radioactive substances?

A

A true exponential

58
Q

Why is the dice decay simulation a good model for the random nature of radioactive decay?

A
  • Cannot predict when dice/atom will decay

- Cannot predict which dice/atom will decay

59
Q

Why do you wear gloves as a safety precaution when handling radioactive material?

A
  • prevents contamination

- which would cause damage/irradiation over a longer period of time

60
Q

What is fusion?

A

The joining of light (low mass) nuclei to form a single more massive nucleus

61
Q

What is fission?

A

The splitting of a massive nucleus to produce two or more lighter nuclei with the release of energy

62
Q

Why is energy released from fusion?

A

Because there is a difference in mass between the reactants and products

63
Q

What are the reactants in fusion?

A

4 protons

64
Q

What are the products in fusion?

A

He-4 atom, 2 positrons, 2 electron neutrinos, gamma radiation and energy

65
Q

How is terrestrial fusion being made possible?

A

-Fusion reactors are being developed that will use hydrogen isotopes (deuterium and triterium) as fuel

66
Q

What are the advantages of terrestrial fusion over fusion in the sun?

A
  • The fusion of deuterium and triterium is achievable at slightly lower temperatures
  • It generates a higher yield (more energy output per kg of fuel)
67
Q

What are fissile materials?

A

Elements which undergo fission

68
Q

What is the most abundant form of Uranium?

A

Uranium-238

69
Q

How is the proportion of fissile Uranium-235 increased?

A

By enriching uranium fuel

70
Q

When does fission spontaneously occur with uranium 235?

A

When the minimum critical mass is reached

71
Q

What does the spontaneous fission of uranium-235 lead to?

A

A chain reaction

72
Q

What does an uncontrolled chain reaction of fission produce?

A

An outpouring of energy (explosion) that can be used to great destructive effect

73
Q

What is done to initiate the fission process?

A

A ‘thermal’ neutron is fired into a Uranium-235 nucleus

74
Q

What does Uranium-236 atom split into during fission?

A

Barium-144
Krypton-89
3 neutrons
(Gamma Radiation and energy)

75
Q

What are the fuel rods in a fission reactors?

A
  • uranium oxide in small pellets

- enriched to about 5% Uranium-235

76
Q

What is the purpose of the moderator and coolant (often water) in a fission reactor?

A
  • moderator slows down neutrons to ensure successful fission events
  • coolant transfers thermal energy away from the core
77
Q

What do the control rods do in a fission reactor?

A

Absorb neutrons to prevent an uncontrolled chain reaction

78
Q

What does the containment vessel in a fission reactor do?

A

Absorb gamma radiation from the reactor core

79
Q

How is the coolant water used to generate electrical energy in a nuclear fission power station?

A
  • Coolant water is used to generate steam
  • The turbines convert linear k.e. of steam to particles into rotational k.e.
  • Coil of wire is turned by turbines in the generator within a strong magnetic field
80
Q

What is irradiation?

A

When an object or person is exposed to ionising radiation

81
Q

What is contamination?

A

When an object or person has particles of radioactive material on or inside it or them

82
Q

Does a person or object become radioactive due to irradaition?

A

No

83
Q

What are the two examples of irradation?

A
  • Radiotherapy

- Sterlization

84
Q

What is radiotherapy?

A

The irradiation of tumours to destroy cells to control growth using a powerful gamma source to produce a narrow beam of radiation

85
Q

What is sterlised with radiation?

A

Food stuffs and medical equipment which cannot be sterlised at high temperatures in water

86
Q

What are the two examples of medical contamination?

A
  • Chemotherapy

- Medical Tracers

87
Q

What is chemotherapy?

A

The ingestion or injection of radioactive sources that target specific cells (rapidly dividing ones) and emit radiation to destroy them

88
Q

What chemicals are typically used in chemotherapy?

A

Site specific ones

89
Q

How do medical tracers work?

A

Radioactive material is ingested and injected to investigate digestive system or circulatory system by tracing the flow of a substance through the organs

90
Q

What type of radiation is used in radiotherapy and why?

A

Gamma since it is the most penetrating ie. can penetrate skin

91
Q

What type of radiation is used in chemotherapy and why?

A

Apha and Beta - less penetrating, delivers energy over a short range and does not leave the body

92
Q

What type of radiation is used in medical tracers? Why?

A

Beta and gamma as they do leave the body so they can be detected externally

93
Q

Why do radioactive materials used in tracers have a fairly short half life?

A

So the patient does not remain contaminated for too long

94
Q

What are the three main industrial uses of radioactive materials?

A
  • Pipe fractures (locating)
  • Thickness control
  • Level control
95
Q

What radiation type is used in finding pipe fractures? WHy?

A

Gamma because it easily penetrates the ground/soil

96
Q

What radiation type is used in thickness control and why?

A

Beta as the intensity of the radiation arriving at the detector would be affected by the thickness of the said material

97
Q

What radiation type is used in level control and why?

A

Beta as the intensity of beta radiation arrivng at the detector drops when the level reaches required value

98
Q

Give three ways in which a worker at a nuclear facility could become contaminated:

A
  • absorbing radioactive particles by the skin
  • breathing in radioactive particles
  • entrance via an open wound
99
Q

Why is radon a particularly harmful radioactive element?

A
  • it is a gas at room temprature so can be inhaled

- emits alpha radiation which is the most ionising nuclear radiation

100
Q

How does protective clothing and a dusk mask prevent contamination?

A
  • prevents the transfer of radioactive atoms to the worker’s skin
  • lungs
  • and their own clothing
101
Q

Why does taking a flight increase your radiation dose?

A
  • cosmic rays are more intense at a higher altitude

- at altitide there is less atmosphere above you to absorb the cosmic rays

102
Q

How do fission products store the energy released by fission?

A
  • as kinetic energy of the fission fragments and the (free) neutrons
103
Q

Why does the temperature of a radioactive core increase when a large number of fission reactions occur?

A
  • products of the fission reactions collide with other atoms in the core
  • and transfer kinetic energy to these atoms
  • raising the temperature
104
Q

How do control rods affect the speed of the chain reaction?

A
  • control rods are made of a material that absorbs neutrons
  • the rods are lowered into the reactor to slow down the chain reaction
  • due to the decrease in the number of neutrons produced from fission available to cause further fission
105
Q

What is the relationship between half life and activity?

A

The shorter the half life, the greater the initial acitivity

106
Q

What is the ratio of net decline?

A

The proportion of the radioactive element left after a certain number of half lives

107
Q

How is gamma radiation detected from medical tracers?

A

using a gamma camera

108
Q

Name natural sources of background radiation:

A
  • radon gas
  • cosmic rays
  • food and drink
  • radiation emitted from ground
109
Q

What does a moderator do in a fission reactor?

A

It is used to slow down the emitted neutrons from the reactions so they are moving at the correct speed to cause more fission reactions

110
Q

What is the purpose of the coolant in the fission reactor?

A

cools the reactor and heats water to produce high-pressure steam

111
Q

Why is a fission reactor contained within a thick steel shell and concrete shield?

A

The steel is to withstand the high temperature and pressure of the core
Concrete is to absorb gamma radiation emmited by the core

112
Q

What is meant by a chain reaction in a fission reactor?

A
  • A series of fission reactions which are caused when
  • The neutrons released from one fission go on to cause more fission reactions when absorbed by a fissionable nucleus
  • which will release even more neutrons and so on
113
Q

What would happen if the fission reactions weren’t controlled by the control rods?

A
  • Without control by the control rods, all the neutrons from each fission would go on to cause further fissions
  • this would happen repeatedly and continuously so a huge amount of energy would be released rapidly in an explosion
114
Q

Where does the energy in the form of radiation come from in a fusion reaction?

A

Loss of mass converted into energy

115
Q

Why have no functioning nuclear fusion reactors been built for commercial use?

A

It has not been possible to create the correct fusion conditions, very high temperature and pressure, for sufficiently long periods of time

116
Q

Why is radon harmful?

A

Since it is a radioactive gas which can be breathed into the lungs and produces the most ionising radition, alpha

117
Q

What are the advantages of nuclear fuel?

A
  • much greater supply of fuel available
  • no radioactive waste produced
  • helium produced (harmless, useful gas)
  • most energy producing efficient process - higher yield
118
Q

What are the disadvantages of nuclear fuel?

A
  • very expensive to construct
  • complex to operate
  • very high temperatures and pressures are hard to reach and maintain
  • workers have less experience of how to operate them

AQA GCSE Physics (9 decks)

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