The atom and radioactivity Flashcards

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1
Q

history of theories on structure of atom

A

Democritus: all matter made up of identical lumps, couldn’t be broken down
John Dalton: each element made up of different type of atom
Thomson: plum pudding theory (sphere of positive charge with negative electrons scattered in it)
Rutherford: mostly empty space, positive charge concentrated at centre of nucleus

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2
Q

Rutherford experiment

A

fired alpha particles at thin sheet of gold
most went through
some bounced right back

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3
Q

nuclide definition

A

atoms comprised of particles number of proton and neutrons

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4
Q

ionisation definition

A

when atom/molecule loses electrons

forms ions

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5
Q

ionising radiation

A

high-energy radiation able to cause atoms/molecules to lose electrons

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6
Q

EM spectrum able to cause ionisation

A

UV
X-rays
gamma rays

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7
Q

radioactive meaning

A

decay and give out ionising radiation to become more stable

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8
Q

nature of different types of radiation

A
alpha = 2 protons, 2 neutrons
beta = electron
gamma = EM wave
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9
Q

charge of different types of radiation

A
alpha = 2+
beta = -1
gamma = 0
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10
Q

mass of different types of radiation

A
alpha = He nucleus (relatively large)
beta = very small (negligible)
gamma = zero
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11
Q

range of different types of radiation

A
alpha = 3-5cm
beta = 2-3m
gamma = 100s of metres
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12
Q

ionising effect of different types of radiation

A
alpha = very strong due to size
beta = moderately ionising
gamma = very weak, tends to pass through rather than interact with particles
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13
Q

penetration of different types of radiation

A
alpha = slow moving, stopped by paper, skin
beta = moderate, blocked by thin plate of metal
gamma = high, blocked by thick metal plates
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14
Q

different types of radiation in magnetic/electric field

A

alpha: larger charge + feels greater force in these fields+ deflected less due to greater mass than beta, deflected in opposite direction to beta
beta: deflected in opposite direction to alpha (opposite charge)
gamma: doesn’t get deflected (no charge)

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15
Q

danger of different types of radiation

A

alpha: most dangerous inside of body due to low penetration power
beta + gamma most dangerous outside due to higher penetration power

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16
Q

why emitting gamma rays doesn’t change element of nucleus

A

gamma ray is just energy

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17
Q

alpha decay

A

atomic number -2

mass number -4

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18
Q

beta decay

A

atomic number +1
mass number 0
neutron turns into proton + electron, electron emitted

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19
Q

background radiation definition

A

low level radiation around us all the time

20
Q

main causes of background radiation

A
natural radioactive substances (rocks, soil, living things, cosmic rays
human activities (nuclear waste, power stations, medical uses of radiation)
21
Q

irradiation uses

A

make medical equipment/food sterile

destroy cancer cells in patients’ bodies

22
Q

alpha radiation uses

A

smoke alarm
alpha radiation ionises air
small electric current flows in smoke detector
in fire, smoke particles absorb alpha radiation
current drops
alarm sets off

23
Q

beta radiation uses

A

monitor thickness of materials
radiation passes through given material
thicker material = more radiation absorbed =less radiation reaches detector
detector on other side sends signals to control unit that adjusts thickness of material

24
Q

gamma rays uses

A
cancer treatment (wide beam focused on tumour to limit damage to healthy cells)
sterilise food / medical equipment (kills pathogens)
25
Q

beta or gamma emitting sources as tracers in medicine

A

diagnostics
tracer swallowed or injected into patient
releases radiation periodically
progress monitored by radiation detector
has to have short half-life so radioactivity disappears quickly

26
Q

beta or gamma emitting sources as tracers in industry

A

radioactive source placed in underground pipes
tracer tracked by detector above ground
leak or blockage shown by reduction in activity

27
Q

carbon dating

A

all organisms have around 1/10000000 of carbon as carbon-14
organisms dies, no more carbon-14 gained from environment
carbon-14 decays with half-life of 5730 years

28
Q

half-life of uranium-238

A

4.5 billion years

29
Q

relative proportions daring

A

radioactive uranium changes into stable lead after series of half-lives
measure relative proportion of uranium and lead isotopes in rock
approximate age can be worked out

30
Q

radiation dose units

A

sieverts (Sv) or millisieverts (mSv)

31
Q

how radioactive materials handled carefully

A

using tongs
holding them far from body as possible
avoid looking at material directly
keep exposure to minimum

32
Q

how radioactive materials stored

A

stored in lead box
lead absorbs alpha and beta radiation
reduces gamma radiation

33
Q

dangers of radiation

A

may cause cancer

radiation sickness

34
Q

fission definition

A

splitting of atom into smaller atoms

35
Q

how fission occurs

A

large isotope bombarded by slow-moving neutron
atom absorbs neutron
nucleus becomes unstable
atom splits into smaller atoms (2-3 high-speed neutrons) and large amount of energy
chain reaction continues

36
Q

how nuclear fission is controlled

A

moderators slow down the produced neutrons

prevents reactor from overheating and exploding

37
Q

nuclear fuel advs

A

small amount of nuclear fuel gives large amount of energy relatively inexpensively

38
Q

how nuclear waste is disposed of

A

low level: bury in secure landfill sites
intermediate level: sealing into concrete blocks, in steel canisters, buried underground
high level: sealed in glass and steel, stored underground, cooled for 50 years, moved to more permanent storage

39
Q

fusion definition

A

joining of 2 lighter atoms into larger atom under extremely high pressure and temperature

40
Q

why nuclear fusion is hard

A

requires high pressure and temperatures

takes a lot of energy (no source on Earth can reach these levels)

41
Q

nuclear fusion uses

A

potential future energy source

hydrogen bombs

42
Q

how fusion works

A

nuclei approach each other and fuse
nuclei repel each other as both positively charged
requires a lot of pressure and temperature to overcome this to fuse
releases enormous amounts of energy with minimal radioactive waste

43
Q

cold fusion

A

2 scientists claimed to undergo fusion in room temp. in 1989

been unable to reproduce this, never been validated

44
Q

half-life of radioactive isotope definition

A

average time taken for number of unstable nuclei to halve

time taken for count rate from original isotope halve

45
Q

radioactive of sample measured in

A

becquerel (Bq)

one nucleus decaying per second

46
Q

radioactivity of sample over time

A

older sample = less radiation