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GCSE Physics > Atomic Structure > Flashcards

Atomic Structure Flashcards

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1
Q

Give an approximation for the radius of an atom.

A

1x10⁻¹⁰ metres

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2
Q

What are the three subatomic constituents of an atom?

A

proton, neutron, electron

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3
Q

Where is most of the mass of an atom located?

A

inside the nucleus

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4
Q

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

A

1/10,000

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5
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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6
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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7
Q

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

A
  • absorbing electromagnetic radiation
  • emitting electromagnetic radiation
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8
Q

What is EM radiation?

A

energy waves

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9
Q

Explain how an atoms electron arrangement changes when it absorbs EM radiation

A

● Electrons move further away from the nucleus
● They move to a higher energy level

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10
Q

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

A

● Electrons move closer to the nucleus
● They move to a lower energy level’s

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11
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

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12
Q

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

A

They all have the same number of protons.

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13
Q

What is the name given to the number of protons in an atom?

A

atomic number

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14
Q

What is the atomic mass number?

A

Number of protons and neutrons in an atom

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15
Q

What is an isotope of an atom?

A

An atom of an element that has a different number of neutrons, but the same number of protons.

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16
Q

How do atoms turn into positive ions?

A

● They lose one or more of their outer electrons
● Electrons are negatively charged, so the resultant charge of the atom is positive

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17
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.

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18
Q

How did the plum-pudding model describe the atom?

A

A ball of positive charge, with negatively charged electrons distributed evenly throughout it.

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19
Q

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

A

The atom was believed to be indivisible.

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20
Q

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

A

Rutherford’s alpha-scattering experiment

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21
Q

What is the name given to the currently accepted model of the atom?

A

The Bohr nuclear model.

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22
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

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23
Q

What reinforces a scientific theory?

A

When experimental results agree with the hypothesised theoretical calculations and theories.

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24
Q

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

A

the existence of neutrons

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25
Q

Why do unstable nuclei give out radiation?

A

● Unstable nuclei undergo decay to become more stable
● As they release radiation their stability increases

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26
Q

What is radioactive decay?

A

The process in which unstable isotopes decay into other elements and emit radiation as they attempt to become more stable

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27
Q

Define the activity of an unstable nucleus

A

Activity is the rate of decay of a source of unstable nuclei.

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28
Q

What is the unit of radioactivity?

A

Becquerel (Bq)

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29
Q

What is count-rate?

A

The number of radioactive decays per second for a radioactive source.

30
Q

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

A

Geiger-Muller tube

31
Q

State four types of nuclear radiation.

A

Alpha particles, beta particles, gamma rays and neutrons

32
Q

What are the constituents of an alpha particle?

A

two protons and two neutrons - the same as a helium nucleus

33
Q

What is the range of an alpha particle through air?

A

A few centimetres (normally in the range of 2-10cm).

34
Q

What will stop beta radiation from passing through a point?

A

● A thin sheet of aluminium
● Several metres of air

35
Q

What will stop gamma radiation from passing through a point?

A

● Several centimetres of lead
● A few metres of concrete

36
Q

Which type of radiation is the most ionising?

A

alpha radiation

37
Q

Which type of radiation is the least ionising?

A

gamma radiation

38
Q

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

A

Both mass and charge remain unchanged.

39
Q

Describe the nature of radioactive decay

A

● Random
● Which nuclei decays and when is determined only by chance
● It is impossible to predict which nuclei will decay and when

40
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

41
Q

What is radioactive contamination?

A

The presence of unwanted radioactive nuclei on other materials.

42
Q

What is irradiation?

A

The process of exposing an object to nuclear radiation. The irradiated object does not become radioactive

43
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

44
Q

Give 4 sources of background radiation

A
  • rocks
  • cosmic rays from space
  • nuclear weapon testing
  • nuclear accidents
45
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.

46
Q

What is the unit used to measure radiation dosage?

A

Sieverts (Sv)

47
Q

How many millisieverts (mSv) make up 1 sievert (Sv)?

A

1000 millisieverts (mSv) = 1 sievert (Sv)

48
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

49
Q

What factors determines how dangerous a particular radioactive isotope is?

A

The half-life of the isotope

50
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

51
Q

State two uses of nuclear radiation in the field of medicine

A
  • examining internal organs
  • controlling and destroying unwanted tissue
52
Q

How is radiation used in sterilisation?

A

Gamma emitters are used to kill bacteria/parasites on equipment.

53
Q

Explain the process of radiotherapy

A

● Gamma emitters direct gamma rays at the cancerous cells
● The cancerous cells absorb the radiation and are killed

54
Q

How are medical tracers chosen?

A

They should have a short half 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.

55
Q

What is nuclear fission?

A

The splitting of a large, unstable nuclei to form smaller more stable nuclei

56
Q

Give an example of fissionable isotope

A

Uranium-235

57
Q

What usually needs to happen to induce fission?

A

● The unstable nuclei must absorb a neutron
● Spontaneous fission (where no neutron absorption occurs) is rare

58
Q

Alongside two smaller nuclei, what else is emitted in a fission reaction?

A

● Two or three neutrons
● Gamma rays
● Energy

59
Q

What forms of energy do all fissions products have?

A

Kinetic energy

60
Q

What takes place during a chain reaction in a nuclear reactor?

A

● An unstable nucleus absorbs a neutron
● The nucleus undergoes fission and releases 2 or 3 further neutrons
● These induce more fission, which results in a chain reaction

61
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 lead to a nuclear explosion

62
Q

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

A

fuel rods, control rods, moderator

63
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.

64
Q

How is the chain reaction in a fission reactor kept under control?

A

● Control rods are positioned in between the fuel rods
● The rate of fission is controlled by moving these rods up and down
● The lower the rods are inserted, the slower the rate of fission

65
Q

What is fissile nuclei?

A

Nuclei in which fission can be induced through the absorption of slow neutrons

66
Q

What is nuclear fusion?

A

The joining of two light nuclei to produce a heavier nuclei and release energy

67
Q

Name two isotopes of hydrogen which are commonly used in nuclear fusion

A

deuterium and tritium

68
Q

Which releases more energy, fusion or fission?

A

nuclear fusion

69
Q

Explain the difficulty of generating energy through nuclear fusion.

A

Fusion requires very high temperatures which in itself requires large quantities of energy and also requires casing which can withstand them.

70
Q

Explain why nuclear fusion is currently not a viable way to produce energy on Earth.

A

With current equipment/techniques, the energy required is greater than the energy produced, resulting in a net energy loss.

GCSE Physics (8 decks)

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