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Atomic Level Radiation Physics > Atomic physics > Flashcards

Atomic physics Flashcards

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1
Q

The higher the binding energy, the ____ stable the nucleus.

A

more

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2
Q

Radioactive atoms are atoms that are:

A

unstable

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3
Q

radioactive nucleii try to inrease binding energy by:

A

radioactive decay

fusion

fission

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4
Q

Nuclear stability depends on the ratio of:

A

neutrons to protons

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5
Q

Unstable nucleii occur when the neutron to proton ration is:

A

too high or too low

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6
Q

the ratio of protons to neutrons tends to be 1:1 for low atomic numbers and closer to ____ for high atomic numbers.

A

2:1, neutrons to protons.

EX: 1.6:1 for led

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7
Q

how is the neutron proton nuclear stability ratio expressed?

A

neutrons (y)/#protons (x)

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8
Q

high atomic numbers are ______ stable.

A

less

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9
Q

What is the mass defect?

A

the atomic mass of the nucleus is less than the mass of the individual protons and neutrons added together. This is on account of binding energy in the nucleus.

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10
Q

What formula demonstrates that mass and energy are equivalent?

A

E=mc^2

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11
Q

What are the fundamental forces of nature from weakest to strongest?

A
  1. gravity
  2. weak nuclear
  3. electric/magnetic
  4. Strong nuclear
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12
Q

What is the force of gravity?

A

the force that binds the solar system

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13
Q

What is the weak nuclear force?

A

weak force in radioactive decay

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14
Q

What is electric/magnetic force?

A

the force that binds atoms

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15
Q

What is the strong nuclear force?

A

the strong force that binds the nucleus

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16
Q

Strong nuclear force is stronger than electromagnetic forces because:

A

it holds the nucleus together despite the repulsion of positive forces within the nucleus.

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17
Q

What is the strong nuclear force?

A

It is the force that holds nucleons together

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18
Q

Force and intensity fall off with the ____ of the distance. Twice the distance means ____ the intensity/force, and three times the distance means ____the intensity/force.

A

inverse square
1/4
1/9

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19
Q

The ____ shell has the highest binding energy.

A

k shell

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20
Q

What is binding energy?

A

the energy required to remove an orbital electron from an atom (ionization)

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21
Q

Binding energy is dependent on electromagentic force, so as distance increases from the nucleus, the binding energy ______.

A

decreases

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22
Q

Higher atomic numbers have higher binding energies because:

A

the have more protons and therefore more positive charge in the nucleus

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23
Q

Excitation requires energy _____.

A

input

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24
Q

Electrons from higher energy shells dropping into lower energy shells have something analgous to _____ energy.

A

potential

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25
all elements with atomic numbers greater than ____ are unstable.
83
26
Radioactivity is when an ____ decays to a ____.
unstable parent to a less unstable daughter or a stable daughter
27
How do radioactive nuclei become more stable?
through radioactive decay
28
What are three forms of radioactive decay?
gamma (energy ejection) alpha (mass ejection) beta (mass ejection)
29
What is the equation of radioactivity? (A)
change in # parent atoms/ change in time ## Footnote (N/t)
30
A large number of parent atoms mean a ____ decay, while a small number of parent atoms means a ____ decay.
fast slow
31
What is the decay constant?
32
How is radioactivity expressed? (Units)
in bequerel (Bq) =1 disintegration per second (dps)
33
What is half life?
The time it takes to reduce radioactivity by exactly 2.
34
What is the radioactivity equation?
35
What is Tao?
Half life specific to that radioisotope. Defined as time fraction remaining is A/A0=.5
36
How is lambda related to Tao? (Radioactive decay rate related to half life)
37
t/Tao is what? How is it useful?
# of half lives
38
Radioactivity and number of parent atoms equations are:
The same
39
_____ is used to calculate cumulative dose equivalents in radiation protection.
Mean life
40
What are two equations for mean life?
41
What are the modes of radioactive decay?
1. alpha 2. electromagnetic decay (gamma and internal conversion) 3.beta minus 4.Beta plus 5.Electron capture
42
What is alpha decay?
emission of a helium ***nuclei*** (2 protons and 2 neutrons but NO electrons) | occurs only for very heavy radionuclides
43
After alpha decay, the parent will be:
a different atom
44
Alpha emissions exist only in ____ energies, which range from ____ MeV. This is based off the difference between the binding energies of parent and daughter nucleus.
discrete; 4-9 MeV
45
How do alpha emissions carry their energy?
Kinetic energy
46
Gamma decay is a _________ transition.
isomeric (only change in energy state)
47
True or false: an isotope may decay only by gamma emmission?
False. Every gamma emission is preceded by electron capture, beta plus, beta minus, or alpha emission
48
Each gamma emission has a __________ energy.
charactersitic, discrete
49
What is internal conversion?
radioactive decay that occurs by: 1. a release of energy from the nucleus that strikes an electron, removing it from orbit (usually k shell) 2. a cascade of elctrons into lower shells, producing characterisitc x rays 3. If these characterisitc x rays interact with any other orbiting electrons and knocks them out of their shell, the ejected electrons will be called Auger electrons
50
What is Beta- decay?
The conversion of a neutron to a proton and an emmission of a beta- particle (identical to an electron but born from the nucleus) that results in a +1 atomic number but no change in atomic mass.
51
Do beta minus emissions have discrete or continuous energies? Why?
continuous. Their values range from 0-the binding energy, and the anti- neutrino (v') compensates for the difference. (beta- + v'=binding energy)
52
When does beta - decay occur?
When there are too many neutrons and not enough protons.
53
When does beta + occur?
When there are too many protons and not enough neutrons
54
What is beta + decay? (aka positron emission)
A proton becomes a neutron and a positive electron (positron) is emitted from the nucleus.
55
What is the threshold in difference between binding energies of parent and daughter required for beta + to occur?
1.02 MeV
56
What is taken in account for conservation of mass and energy in beta +?
neutrino
57
Beta - involve , _ while beta + involve _ as it relates to conservation of energy from binding energy.
anti-neutrino (v') neutrino (v)
58
electron capture and _ are competing decays.
beta + decay
58
What is electron capture?
an inner shell electron is absorbed into the nucleus, combines with a proton to become a neutron. It has the same result as beta + decay, except it is also accompanied by charactersitic x rays.
59
When does electron capture occur?
When there are too many protons and not enough neutrons
60
What are the three types of compound radioactive decay?
1. secular 2. transient 3. no equilibrium
61
When does secular equillibrium occur?
When the half life of the parent is MUCH greater than the half life of the daughter (10,000 times greater or more) so large that its activity can be considered constant over many daughter half lives
63
This is an example of what kind of compound decay?
Secular equilibrium
64
When does transient equilibrium occur?
When the half life of the parent is about 10 times greater than the half life of the daughter. Daughter activity increases as amount of daughter increases.
65
In transient equilibrium, after about 4 daughter half lives, what will happen?
Activity of parent will = activity of daughter.
66
This is an example of what kind of compound decay?
Transient equilibrium
67
What must be true for no equilibrium compound decay to occur?
The daughter half life must be greater than the parent half life.
68
What kind of compound decay is this?
No equilibrium
69
What happens in nuclear fission?
a high atomic target (such as Uranium 235) is struck with an incident neutron that breaks the nucleus in two and loose neutrons
70
What changes occurs to bremsstrahlung vs charactersitic x rays with an increase in kvp?
no change to charactersitic maximum brem energy increases to set kvp
71
What happens with an increase in mA?
energies do not change, but the NUMBER of photons increase proportionally
72
Beam intensity depends on:
kVp mA target material filtration
73
scatter decreases when the beam is narrowed or made broader by the collimators?
narrowed
74
For a monoenergetic beam, the first half value layer_()_the second half value layer. For a poly energetic beam, the first half value layer_____()_-__the second half value layer.
equals is less than
75
What is the equation for half value layer?
HVL= .693/ u | u=linear attenuation coefficient
76
What is the attenuation equation? What can it be used for?
Only for mono energetic beams

Atomic Level Radiation Physics (1 decks)

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