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BMAT Physics > The atom and radioactivity > Flashcards

The atom and radioactivity Flashcards

(46 cards)

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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

Study These Flashcards
A

low level radiation around us all the time

20
Q

main causes of background radiation

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

irradiation uses

Study These Flashcards
A

make medical equipment/food sterile

destroy cancer cells in patients’ bodies

22
Q

alpha radiation uses

Study These Flashcards
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

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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

Study These Flashcards
A 
cancer treatment (wide beam focused on tumour to limit damage to healthy cells)
sterilise food / medical equipment (kills pathogens)
25
beta or gamma emitting sources as tracers in medicine
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
beta or gamma emitting sources as tracers in industry
radioactive source placed in underground pipes tracer tracked by detector above ground leak or blockage shown by reduction in activity
27
carbon dating
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
half-life of uranium-238
4.5 billion years
29
relative proportions daring
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
radiation dose units
sieverts (Sv) or millisieverts (mSv)
31
how radioactive materials handled carefully
using tongs holding them far from body as possible avoid looking at material directly keep exposure to minimum
32
how radioactive materials stored
stored in lead box lead absorbs alpha and beta radiation reduces gamma radiation
33
dangers of radiation
may cause cancer | radiation sickness
34
fission definition
splitting of atom into smaller atoms
35
how fission occurs
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
how nuclear fission is controlled
moderators slow down the produced neutrons | prevents reactor from overheating and exploding
37
nuclear fuel advs
small amount of nuclear fuel gives large amount of energy relatively inexpensively
38
how nuclear waste is disposed of
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
fusion definition
joining of 2 lighter atoms into larger atom under extremely high pressure and temperature
40
why nuclear fusion is hard
requires high pressure and temperatures | takes a lot of energy (no source on Earth can reach these levels)
41
nuclear fusion uses
potential future energy source | hydrogen bombs
42
how fusion works
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
cold fusion
2 scientists claimed to undergo fusion in room temp. in 1989 | been unable to reproduce this, never been validated
44
half-life of radioactive isotope definition
average time taken for number of unstable nuclei to halve | time taken for count rate from original isotope halve
45
radioactive of sample measured in
becquerel (Bq) | one nucleus decaying per second
46
radioactivity of sample over time
older sample = less radiation

BMAT Physics (7 decks)

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