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[GCSE] physics > P4: Atomic Structure > Flashcards

P4: Atomic Structure Flashcards

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1
Q

Explain how the properties of alpha, beta, gamma radiation affects the level of the hazard at different distances (4)

A
  • At short distances, the most hazardous radiation would be alpha radiation
  • as it has the highest ionizing power
  • at long distances gamma radiation would be the most hazardous
  • as it has the highest penetrating power
  • medium distance: beta is more hazardous than gamma as it has a higher ionizing power but less hazardous than alpha
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2
Q

Give 4 sources of background radiation (natural + man-made

A

natural:
- rocks
- cosmic rays from space
man-made:
- nuclear power / weapons
- medical imaging

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3
Q

Define background radiation

A
  • low-level radiation that is around us all the time
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4
Q

What is the unit used to measure radiation dosage?

A
  • sieverts (Sv)
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5
Q

What factor determines how dangerous a particular radioactive isotope is?

A
  • the half life of the isotype
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6
Q

What factor determines how dangerous a particular radioactive isotope is?

A
  • the half-life of the isotype
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7
Q

Why are isotypes with long half-lives particularly harmful?

A
  • they remain radioactive for much longer particularly periods of time
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8
Q

State two uses of nuclear radiation in the field of medicine

A
  1. Examining of internal organs
  2. Controlling and destroying unwanted tissue
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9
Q

State a use for each type of radiation

A

alpha: smoke detectors
beta: used in medical tracers to explore internal organs
gamma: treat cancer cells or sterilisation

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10
Q

Explain the process of radiotherapy using gamma radiation

A
  • gamma emitters direct gamma rays at the cancerous cells
  • the cancerous cells absorb the radiation and are killed
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11
Q

Describe how radioactive tracers’ work (4)

A
  • patients drink a small amount of radioactive isotype that emits ionizing radiation (beta or gamma)
  • the tracer passes through the organ
  • if the organ is healthy, the tracer will flow through it in the blood
  • if the organ is blocked, the tracer will be stopped, and radiation will be detected for longer
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12
Q

give 4 properties a medical tracer must have to be chosen

A
  • must emit radiation that can be detected (high penetrating power) from outside the body
  • must not be strongly ionizing to minimize damage to the body tissue
  • must have a short half life
  • must not decay into another radioactive isotype
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13
Q

Describe how nuclear radiation is used to destroy a tumor using a radioactive implant. Include details about half life (4)

A
  • small implant of radioactive isotype placed in tumor
  • radiation from isotype destroys cancer cells
  • use isotype with short half-lives to ensure healthy cells are not damaged
  • do not make half times too short otherwise the radiation would not have time to kill cancer cells
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14
Q

Explain why the source chosen for a tracer should have a short half life (2)

A
  • as short half-life means the level or radiation
  • decreases rapidly
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15
Q

How can workers reduce their exposure to radiation (2)

A
  • protective clothing such as lead lines coats
  • reduce exposure times
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16
Q

Describe the process of nuclear fusion (4)

A
  • an unstable nucleus
  • must absorb a neutron
  • the nucleus splits into two smaller nuclei
  • and releases 2 or 3 neutrons and energy
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17
Q

What is a chain reaction in terms of nuclear fission?

A
  • when the neutrons released in a fission reaction cause further fission reations
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18
Q

Describe a chain reaction in terms of nuclear fission

A
  • each released neutron from nuclear fission, if travelling at the right slow speed, can be absorbed by another nucleus causing further fission reactions
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19
Q

What is the consequence of an uncontrolled chain reaction

A
  • the rate of fission events becomes to high and results in the production of too much energy
  • this can led to a nuclear explosion
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20
Q

What are the three main components of the core a nuclear reactor?

A
  1. fuel rods
  2. control rods
  3. moderator
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21
Q

What is the role of the moderator in a nuclear reactor?

A
  • to slow down the neutrons so they are travelling at speeds which allow them to be absorbed by fissile nuclei and cause fission
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22
Q

Why is the reactor in a thick steel vessel, surrounded by concrete ( 2 )

A
  • to withstand the high temperature and pressure in the nuclear reactor core
  • steel absorbs any ionising radiation that escapes
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23
Q

Explain what happens in the process of nuclear fusion (3)

A
  • light nuclei
  • join to form a heavier nucleus
  • mass of the nuclei is converted to energy
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24
Q

give the approximation for the radius of an atom

A

1 x 10 “ -10 metres

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25
Q

What are the three subatomic constituents of an atom

A
  1. proton
  2. neutron
  3. electron
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26
Q

where is the mass of an atom mostly concentrated

A

in the nucleus

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27
Q

Approximately what proportion of the total radius of an atom is the radius of the nucleus

A

1/ 10,000 metres

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28
Q

Describe the arrangement of protons , neutrons and electrons in an atom

A
  • the protons and neutrons are found in the atom’s nucleus
  • the electrons are found in discrete energy levels around the nucleus
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29
Q

what type of charge does the nucleus of an atom have? Why?

A
  • positive charge
  • the nucleus contains protons and neutrons
  • protons have a positive charge
  • neutrons have no charge
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30
Q

Give two ways that an atom’s electron arrangement can be changed

A
  1. Absorbing electromagnetic radiation
  2. Emitting electromagnetic radiation
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31
Q

Explain how an atom’s electron arrangement changes when it absorbs EM radiation.

A
  • electrons move further from the nucleus
  • to a higher energy level.
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32
Q

Explain how an atom’s electron arrangement changes when it emits EM radiation.

A
  • electrons move closer to the nucleus
  • to a lower energy level.
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33
Q

How does the ratio of electrons to protons in an atom result in the atom having no overall charge?

A
  • the number of protons is equal to the number of electrons
  • protons and electrons have equal and opposite charges, so charge cancels out
34
Q

What do all forms of the same element have in common?

A
  • they all have the same number of protons
35
Q

what is the atomic number

A

the number of protons in an atom

36
Q

what is the mass number ?

A
  • the total number of protons and neutrons in the atom
37
Q

what is an isotope of an atom?

A
  • an atom of an element that has the same number of protons but different numbers of neutrons
38
Q

how do atoms turn into positive ions?

A
  • they lose one or ore of their outer elcteons
  • electrons are negatively chatged, so the resultant charge of the atom is postive
39
Q

What may lead to a scientific model being changed or replaced?

A
  • the discovery of new experimental evidence which doesn’t agree with the existing theory
40
Q

How did the plum-pudding model describe the atom?

A
  • a ball of positive charge, with negatively charged electrons distributed evenly throughout it
41
Q

Prior to the discovery of the electron, what was believed about the atom?

A
  • the atom was believed to be indivisible
42
Q

what experiment led to the plum-pudding model being discarded?

A

Rutherford’s alpha scattering experiment

43
Q

What is given to the currently accepted model of the atom

A
  • The Bohr nuclear model
44
Q

State the conclusions of the Alpha-Scattering experiment

A
  • most of the mass of the atom is concentrated at the centre in the nucleus
  • the nucleus is positively charged
45
Q

What reinforces a scientific theory?

A
  • when experimental results agree with the hypothesised theoretical calculations and theories
46
Q

What did James Chadwick’s experiments on the atom prove?

A
  • the existence of neutrons
47
Q

How did Niels Bohr adapt this
model? ( The Alpha Scattering experiment)

A

He suggested that electrons orbit the nucleus at specific distances

48
Q

Why do unstable nuclei give out radiation?

A
  • unstable nuclei undergo decay to become more stable
  • as they release radiation their stability increases
49
Q

what is radioactive decay?

A

when unstable nuclei give out radiation to become more stable

50
Q

Define the term ‘ activity ‘ of an unstable nucleus

A

activity is the rate of decay of a source of unstable nuclei

51
Q

What is the unit for radioactive activity?

A
  • Becquerel (Bq)
52
Q

define ‘ count-rate’?

A
  • the number of radioactive decays per second for a radioactive source
53
Q

Give an example of a detector that may be used to measure count-rate

A

Geiger-Muller tube

54
Q

State 4 types of nuclear radiation

A
  1. Alpha particles
  2. Beta particles
  3. Gamma rays
  4. Neutrons
55
Q

what are alpha particles made up of and give the range of an alpha particle through air?

A
  • two protons and two neutrons
  • it is the same as the helium nucleus
  • a few centimetres of air
56
Q

what are beta particles and what will stop it from passing through a point

A

– a high speed electron
- ejected from the nucleus as a neutron turns into a proton
- a thin sheet of aluminium/ several metres of air

57
Q

What does gamma radiation consist of and what will stop it from passing through a point?

A
  • a gamma ray (γ) – electromagnetic radiation
    from the nucleus
  • several cm of lead / a few metres of concrete
58
Q

which type of nuclear radiation is
the most and least ionising?

A

Most ionising - alpha
slightly ionising - beta
least ionising - gamma

59
Q

State any changes to mass or charge that occur due to the emission of a gamma ray

A

both mass and change remain unchanged

60
Q

Describe the nature of radioactive decay

A
  • random
  • the nuclei which decays and when is determined only by chance
  • it is impossible to predict which nuclei will decay and when
61
Q

Define the half-life of a radioactive isotope

A
  • the time it takes for the number of unstable nuclei in a substance to halve
  • the time it takes for the count-rate from a sample to fall to half its initial level
62
Q

what is radioactive contamination?

A
  • the presence of unwanted radioactive nuclei on other materials
63
Q

what is irradiation?

A
  • the process of exposing a material to nuclear radiation
  • the material does not become radioactive
64
Q

why is it important for the results of studies on the effects of radiation to be published and shared with other scientists?

A
  • to allow the findings to be independently checked
  • this is known as peer review
65
Q

. State a use of alpha particles:

A

They are used in smoke alarms, as smoke
particles will stop alpha particles from reaching a detector

66
Q

State a use of beta particles:

A
  • Thickness monitoring of paper or aluminium
    sheets.
  • The beta must be able to pass through the sheet to be detected and different amounts will be detected if the sheet is too thin or too thick.
67
Q

State a use for gamma rays:

A

They have several uses in medicine; the kill
cancer cells, to sterilise medical equipment and in radioactive tracers

68
Q

why is ionising radiation dangerous ?

A

It can damage the DNA in cells which can cause them to replicate uncontrollably into tumours

69
Q

Give 4 sources of background radiation

A
  1. Rocks
  2. Cosmic rays from space
  3. Nuclear weapon testing
  4. Nuclear accidents
70
Q

How should background radiation be dealt with in calculations?

A

The background count should be subtracted from any readings before calculations ( half life etc.) are attempted

71
Q

what is the unit used to measure radiation dosage?

A

Sieverts ( Sv)

72
Q

Why might the radiation dosage that different people experience differ?

A
  • some occupations involve working with radiation
  • background radiation differs with location due to things such as the locality of nuclear power stations or radiation related testing
73
Q

Which factor determines how dangerous a particular radioactive isotope is?

A
  • the half-life of the isotope
74
Q

Why are isotopes with long half-lives particularly harmful?

A
  • they remain radioactive for much longer periods of time
  • they must be stored in specific ways to avoid humans and the environment from being exposed to radiation for too long
75
Q

rab

A

bles

76
Q

How is radiation used in sterilisation?

A
  • gamma emitters are used to kill bacteria/ parasites on equipment
77
Q

i do not

A

consent

78
Q

How are medical tracers chosen?

A
  • they should have a short life and decay into a stable isotope which can be excreted
  • they should only release gamma radiation since it is weakly ionising and can easily pass through body tissue without damaging it
79
Q

How is an alpha particle represented in a nuclear equation

A

4 He
2

80
Q

how is a beta particle represented in a nuclear equation?

A

0 e
-1

81
Q

What changes to the nucleus does
emission of nuclear radiation cause?

A

Changes to the mass and/or charge of the
nucleus.

[GCSE] physics (9 decks)

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