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Physics > Atomic Structure and Radiation > Flashcards

Atomic Structure and Radiation Flashcards

1
Q

what is the charge of a proton

A

+1

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2
Q

what is the mass of a proton

A

1

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3
Q

what is the charge of a neutron

A

0

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4
Q

what is the mass of a neutron

A

1

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5
Q

what is the charge of an electron

A

-1

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6
Q

what is the mass of an electron

A

1/2000 of a protons mass

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7
Q

what was the arrangement of john daltons atom

A

tiny spheres
cannot be divided
everything is made from them

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8
Q

what are the names of atom discoverers in order

A

john dalton
jj thompson
ernest rutherford
niels bohr

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9
Q

what was jj thompsons atom like

A

plum pudding - positively charged matter spread with electrons buried
discovered the electron
mass is spread throughout the atom
charge is spread throughout the atom

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10
Q

what is ernest rutherford atom like

A

alpha particles fired at gold nuclei
most of alpha particles passed through = most of the atom is empty space
some alpha particles are deflected through a big angle = nucleus has a large positive charge
only a small number of particles rebound backwards = nucleus of atom is very small

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11
Q

what is neil’s bohrs atom like

A

discovered shells
electrons orbit the nucleus at set distances and with a specific amount of energy
electrons move from one level to another by absorbing and emitting electromagnetic radiation

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12
Q

what is the mass number

A

number of protons and neutrons inside the nucleus

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13
Q

what is the atomic number / proton number

A

number of protons in the nucleus

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14
Q

what is an ion

A

an atom that gets charge by gaining or losing electrons

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15
Q

when is a negative ion formed

A

when the number of protons minus the number if electrons is a minus number

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16
Q

when is a positive ion formed

A

when the number of protons minus the number of electrons is positive

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17
Q

what happens when an unstable nucleus emits radiation

A

it is said to decay

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18
Q

what is activity

A

number of decays measured per second

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19
Q

what is activity measured in and by

A

becquerets , with a geiger counter

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20
Q

when will a nucleus emit radiation

A

you cannot say, it is a random event that happens without anything being done to the nucleus

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21
Q

what are the four types of radiation

A

alpha
beta
gamma
neutrons

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22
Q

what is the nature of alpha

A

particle

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23
Q

what is an alpha particle made up of

A

two protons
two neutrons (helium nucleus)

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24
Q

what is alphas range in air

A

2-3cm

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25
Q

what is alpha absorbed by

A

paper

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26
Q

what is alphas ionising ability

A

the most out of the three types

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27
Q

what is the nature of beta

A

particle

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28
Q

what is beta made up of

A

fast moving electrons

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29
Q

what is betas range in air

A

1-2m

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30
Q

what is beta absorbed by

A

o.5cm of aluminium

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31
Q

what is betas ionising ability

A

middle of the three types

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32
Q

what is the nature of gamma

A

wave

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33
Q

what is gamma made up of

A

high energy electromagnetic wave

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34
Q

what is gammas range in air

A

unlimited

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35
Q

what is gamma absorbed by

A

2-3cm of lead or 1-2m of concrete

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36
Q

what is gammas ionising ability

A

least of three types

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37
Q

when is a beta particle emitted

A

when a neutron in a nucleus decays into a proton

38
Q

what happens when gamma radiation is emitted

A

there is no change to the make up of the nucleus so a new element isn’t formed

39
Q

what is radioactive decay (description not definition)

A

random and spontaneous

40
Q

what are the two half life definitions

A

the time it takes the number of radioactive nuclei in a sample to decrease by 50%
the time it takes the count rate from a radioisotope to decrease by 50%

41
Q

why is radiation dangerous

A

it is able to knock electrons out of atoms

42
Q

what are the dangers of radioactive substances

A

can contaminate other materials they come in contact with
ionisation can damage or kill cells
damage to the genes in a cell can cause mutations and cancer

43
Q

what does irradiate mean

A

exposed to radiation but does not become radioactive

44
Q

what does contaminate mean

A

exposed to radiation and becomes radioactive

45
Q

radius of an atom

A

1 x 10 ^-10

46
Q

how much smaller is the radius of the nucleus of an atom than the radius of the atom

A

10,000 x smaller

47
Q

where is the mass of the atom concentrated

A

the nucleus

48
Q

what are isotopes

A

atoms of the same element but with different masses, which have the same protons but different number of neutrons

49
Q

what happens when electrons move to a higher orbit

A

the atom has absorbed EM radiation

50
Q

what happens when the electrons fall to a lower orbit

A

the atoms have emitted EM radiation

51
Q

what happens if an electron gains enough energy

A

it can leave the atom to form a positive ion

52
Q

what was the problem with the rutherford model?

A

if rutherford was right, the electrons in the cloud close to the nucleus would get attracted and cause the atom to collapse

53
Q

what causes a nucleus to give out radiation

A

unstable nuclei

54
Q

why do nuclei give out radiation

A

to become more stable

55
Q

what is the name of the process where a nucleus gives out radiation to become stable

A

random process called radioactive decay

56
Q

what is activity

A

the rate at which a source of unstable nuclei delays

57
Q

what is the rate of nuclei decay measured in

A

becquerel (Bq)

58
Q

what is count rate?

A

the number of decays recorded by a detector per second

59
Q

what is half life of an isotope? (both definitions )

A

the time taken for half the nuclei in a sample to decay

time taken for the activity or count rate of a sample to decay by half

60
Q

what cannot be predicted ? ( nuclei decay)

A

when any one nucleus will decay

61
Q

what is the impact of the half life being constant

A

it enables the activity of a very large number of nuclei to be predicted during the decay

62
Q

what does a short half life mean

A

-the source has less risks as it does not remain strongly radioactive
- this means initially it is very radioactive but dies down
- it presents less of a risk long term

63
Q

what does a long half life mean?

A

-the source remains weakly radioactive for a long time

64
Q

what is the half life of americium?

A

432 years

65
Q

what is americium used in

A
  • smoke alarms
66
Q

why is americium used as a smoke alarm

A

it is an alpha emitter

67
Q

how is americium used in smoke alarms

A
  • it is emitted into the air around the alarm and does not reach far because alpha is weakly penetrating
    -if smoke reaches the alarm, the amount of alpha particles in the surrounding air drops
    -this causes the alarm to make a sound
68
Q

why is americium suitable for smoke alarms

A

it will not need to be replenished
weak activity wont be harmful to anyone

69
Q

what is contamination

A

the unwanted presence of radioactive atoms on other materials

70
Q

what is the hazard of contamination?

A

the decaying of the contaminated atoms releasing radiation

71
Q

what is irradiation

A

exposing an object to nuclear radiation but not making it radioactive

72
Q

why are medical items irradiated

A

to kill bacteria on its surface

73
Q

what is background radiation

A

weak radiation that can be detected from natural/ external sources

74
Q

which natural sources can background radiation be from?

A

-cosmic rays
-radiation from underground rocks
-nuclear fallout
-medical rays

75
Q

what can affect the level of background radiation?

A

occupation and or location

76
Q

what is the measurement of radiation dose

A

Sieverts (Sv)

77
Q

what is technetium used as?

A

a medical tracer

78
Q

what features make technetium be used as a medical tracer?

A

-half life of 6 years
-decays into a safe isotope that can be excreted by the body
-its injected/swallowed so there is enough time for it to be detected before it decays away and is present for a short enough time to minimise harm from radiation
- gamma emitter so can pass through the body tissue without being absorbed

79
Q

how is radiation used in chemotherapy

A

-gamma emitters are used to emit gamma rays which are directed onto areas of the body with cancer cells , which absorb the energy and die controlling the disease
-it is used to control other unwanted tissue
-as it is hard to direct , surrounding healthy cells can be irradiated and cause side effects

80
Q

what is nuclear fission?

A

the splitting of a large and unstable nucleus

81
Q

what is usually needed for nuclear fission to occur

A

the unstable nucleus must first absorb a neutron

82
Q

what happens when the unstable nuclei absorb a neutron

A

it splits into two smaller nuclei (equal size) and emits two or three neutrons and gamma rays

83
Q

how is energy released (nuclear fission)

A

by the fission reaction

84
Q

what happens in the process of nuclear fission

A

the neutron may collide with another radioactive nucleus
this nucleus absorbs the neutron and becomes unstable
this nucleus splits releasing another neutron and producing more energy

85
Q

how is nuclear fission a chain reaction

A

as energy is being released and one split causes another to occur

86
Q

why does a neutron need to be absorbed before it splits

A

it needs extra energy before it can split and release lots of energy

87
Q

what happens if the chain reaction is not controlled?

A

it will increase at an exponential rate

88
Q

what is nuclear fusion

A

when two small nuclei fuse to form a heavier nucleus releasing lots of energy

89
Q

the sum of…

A

the masses of the two nuclei is more than the mass of the heavier nucleus

90
Q

what happens to some of the mass (nuclear fusion)

A

converted into energy (released as radiation)

91
Q

what is an example of a natural fusion reactor

A

the sun

92
Q

what is the benefit of fusion over fission

A

fusion would be a more efficient way of producing energy compared to fission but there is no design that could accomplish positive net energy on earth

Physics (19 decks)

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