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let's get physical! > 11. Nuclear radiation [COMPLETE] > Flashcards

11. Nuclear radiation [COMPLETE] Flashcards

1
Q

What is the difference in mass when the total mass of a nucleus is less than the sum of its constituent nucleons also known as?

A

Mass defect or mass deficit

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2
Q

What is mass defect or mass deficit defined as?

A

The difference between the measured mass of a nucleus and the sum total of the masses of its constituents

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3
Q

What is mass-energy equivalence?

A

E=mc^2
Mass can be converted into energy
Energy can be converted into mass

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4
Q

What does a mass defect imply?

A

The mass lost if released as energy.

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5
Q

What is binding energy defined as?

A

The energy required to break a nucleus into its constituent protons and neutrons

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6
Q

Is the formation of a nucleus from its constituent nucleons an exothermic or endothermic reaction?

A

The reaction releases energy hence exothermic reaction

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7
Q

What is one unified atomic mass unit or 1u defined as?

A

The mass of exactly 1/12th of a carbon-12

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8
Q

What is 1u equivalent to in MeV?

A

1u = 931.5 MeV

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9
Q

What do you look at when comparing stability of different nuclei?

A

The binding energy per nucleon

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10
Q

What is the binding energy per nucleon defined as?

A

The binding energy of a nucleus divided by the number of nucleons in the nucleus

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11
Q

What does a high binding energy per nucleon indicate?

A

A higher stability since it requires more energy to pull the nucleus apart

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12
Q

What is the most stable element?

A

Iron with a mass number of 56 and the highest binding energy per nucleon

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13
Q

Give the sketch of the graph of the binding energy per nucleon against nucleon number

A
  • Anomaly at He-4
  • Don’t start at 0, no such nuclei exist
  • Axes and units (MeV)
  • Peak at Fe-56
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14
Q

What are the trends and anomalies of the binding energy per nucleon against nucleon number graph?

A
  • At low mass numbers: lower binding energy per nucleon, hence, they are generally less stable.
  • At high mass numbers: general binding energy per nucleon is high and gradually decreases as mass number increases, hence, more unstable.
  • Helium-4, Carbon-12 and Oxygen-16 do not fit into the trends: He-4 is v. stable as it has a high binding energy per nucleon. C-12 & O-16 can be considered as 3 and 4 He-4 bound together.
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15
Q

What element are likely to undergo FUSION and why?

A

The lightest elements (before iron) as their nuclei tend to have a lower binding energy per nucleon, hence, they are generally less stable and have weaker electrostatic forces.

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16
Q

What element are likely to undergo FISSION and why?

A

The heaviest elements (after iron) as they are the most unstable.

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17
Q

What is fusion defined as?

A

When small nuclides that combine together to make larger nuclei, releasing energy

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18
Q

What are the conditions for fusion?

A
  • Both nuclei must have high K.E. to over come electrostatic repulsion between protons.
    • achieved in a star’s core
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19
Q

Outline the process of hydrogen burning

A

1: 2 protons fuse → 1 proton, 1 neutron + 1 positron, 1 neutrino
2: a proton and the deuterium nucleus join to make He-3
3: 2 He-3 fuse → He-4 + 2 protons ejected

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20
Q

What is background radiation is defined as?

A

Low levels of radiation from environmental sources, which are always present around us

21
Q

What is radiation measured in?

A

Counts per second in a unit called Becquerel (Bq)

22
Q

What are the two types of background radiation?

A
  • Natural sources (rocks, cosmic rays)
  • Man-made sources (radon gas, building materials)
23
Q

What is the corrected count rate?

A

When we account for the background radiation and subtract it from the readings we taken.

24
Q

How does a radiation detector detect radiation?

A
  • When alpha or beta radiation pass close to an atom, they can deliver enough energy to remove electrons, ionising the atom
  • Radiation detectors work by detecting the presence of either these ions, or the chemical changes that they produce
25
Q

What are radioactive nuclei?

A

When unstable nuclei emit particles and/or EM radiation to become stable

26
Q

What are alpha particles?

A

Alpha (α) particles are high energy particles made up of 2 protons and 2 neutrons

4
α
2

27
Q

What emits alpha particles?

A

Usually emitted from nuclei that ar very large.

28
Q

What are beta(-) particles?

A

Beta (β−) particles are high energy electrons emitted from the nucleus

0
β
-1

29
Q

What emits beta(-) particles?

A

Nuclei that have too many neutrons

30
Q

How ionising are beta particles?

A

They are moderately ionising due it having a charge of +1e, meaning it can do some slight damge to cells.

31
Q

How penetrating are beta particles?

A

They are moderately penetrating, having a range of around 20 cm - 3 m in air, depending on their energy and can be stopped by a few millimetres of aluminium foil

32
Q

What are gamma rays?

A

Gamma (γ) rays are high energy electromagnetic waves (less than 10^-10)

0
γ
0

33
Q

What emits gamma rays?

A

Nuclei that needs to lose some energy

34
Q

How ionising are gamma rays?

A

Very ionising, can knock out electrons, cause chemical changes in materials, can damage or kill living cells

35
Q

What is a beta(+) particle?

A

A high energy positron

36
Q

Give the general equation for alpha decay

A

A A-2 4
X → Y + α
Z Z-2 2

37
Q

Give the general equation for beta minus decay

A

A A 0
X → Y + β
Z Z+1 -1
OR
A A
X → Y + e- + antineutrino
Z Z+1

38
Q

Give the general equation for beta plus decay

A

A A 0
X → Y + β
Z Z-1 +1
OR
A A
X → Y + e+ + neutrino
Z Z-1

39
Q

Give the general equation for gamma decay

A

A A 0
X → Y + γ
Z Z 0

40
Q

What is radioactive decay is defined as?

A

The random spontaneous decay of a unstable nucleus to form a more stable nucleus, resulting in the emission of an alpha, beta or gamma particle

41
Q

What is a spontaneous process is defined as?

A

A process which cannot be influenced by environmental factors

42
Q

What is a random process is defined as?

A

A process in which the exact time of decay of a nucleus cannot be predicted

43
Q

Is it possible to predict how many nuclei decay in a given time?

A

Yes as the chance to decay is a constant probabality

44
Q

What s the average decay time?

A

The average number of nuclei which are expected to decay per unit time

45
Q

What is the decay constant (λ) is defined as

A

The probability, per second, that a given nucleus will decay

46
Q

What is activity?

A

The number of decays per unit time

47
Q

What is activity measured in?

A

Becquerels (Bq) = one decay per second, or 1 s-1

48
Q

What is half-life is defined as?

A

The time taken for half the number of nuclei in a sample to decay

49
Q
A

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