radioactivity Flashcards
(60 cards)
1
Q
relative change of a proton
A
1+
2
Q
relative charge of a neutron
A
0
3
Q
relative charge of an electron
A
1-
4
Q
relative mass of a proton
A
1
5
Q
relative mass of a neutron
A
1
6
Q
relative mass of an electron
A
0.0005
7
Q
location of proton
A
nucleus
8
Q
location of neutron
A
nucleus
9
Q
location of electron
A
shells around nucleus
10
Q
what does the atomic number tell you?
A
number of protons/electrons
11
Q
what does the mass number tell you?
A
number of protons + neutrons
12
Q
is the atomic number the top or bottom number?
A
bottom
13
Q
is the mass number the top or bottom number?
A
top
14
Q
what are isotopes?
A
elements with the same number of protons but different number of neutrons, so the mass numbers are different
15
Q
what is an alpha particle?
A
a helium nucleus emitted from an unstable nucleus
16
Q
what does a nucleus mean?
A
2 protons and 2 neutrons
17
Q
what is beta minus radiation?
A
an electron emitted from a nucleus
18
Q
what is beta plus radiation?
A
a positron (positive electron)
19
Q
what is a gamma ray?
A
high energy electromagnetic wave
20
Q
decay:
A
- a nucleus can be stable or unstable
- if it is unstable it tries to become more stable by either ejecting mass (alpha or beta) or energy (gamma)
- we call these atoms radioactive
- the process of ejecting radiation is called decay
- decay is random, you cannot predict when it will happen
21
Q
alpha particle equation:
A
(_2^4)α
22
Q
beta minus equation:
A
(_-1^0)β
23
Q
beta plus equation:
A
(_1^0)β
24
Q
what happens in neutron decay?
A
a neutron is emitted by an unstable nucleus
25
neutron decay equation:
(_0^1)n
26
gamma decay equation:
(_0^0)γ
27
how ionising is alpha?
very ionising
28
how penetrating is alpha and what can it be stopped by?
not very penetrating
can be stopped by paper
29
how ionising is beta?
moderately ionising
30
how penetrating is beta and what can it be stopped by?
moderately penetrating
can be stopped by aluminium
31
how ionising is gamma?
not very ionising
32
how penetrating is gamma and what can it be stopped by?
very penetrating
stopped by lead
33
what is a GM tube
a device that detects radiation
34
what happen when radiation comes into contact with photographic film?
the photographic film darkens, showing the presence of radiation
35
how does the GM tube show there's radiation present
a click/beep
36
background radiation:
- food and drink (radioactive isotopes decay overtime)
- nuclear power (from power stations and bombs)
- medical (x-rays, gamma ray scans, cancer treatments, sterilisations)
- radon gas (produced by rocks containing small amounts of uranium)
- cosmic rays (radiation from space, produced in stars)
37
describe how someone should use a GM tube to compare the count-rates from two different radioactive rocks:
- measure background count
- put source close to tube
- remove first rock and measure the counts for the second
- measure both rocks for the same time and distance
- minus background from counts
- repeat and take an average
38
describe how you could investigate which type of potato was more radioactive using a GM tube
- measure background count
- put sources close to the tube
- measure sources separately, but for the same time and distance
- minus background from count
- repeat and take average
39
what is half life?
time taken for half the undecided nuclei to decay
OR
time taken for activity to half its original value
40
to find the number of undecayed nuclei in a sample
1. state the start number
2. go forward a half-life, halving the sample size
3. repeat until the target time has passed
41
to find the age of an isotope:
1. find the total number in the current sample
2. go back a half life, doubling the sample size
3. repeat until all of the sample is the radioactive isotope
42
what precautions are taken when using radioactive sources:
- keeping radioactive sources shielded when not in use (e.g. in a lead-lined box)
- wearing protective clothing to prevent the body becoming contaminated
- limiting exposure time -> less time is spent with radioactive sources
- handling radioactive sources with tongs to increase distance from them
- monitoring exposure using detector badges
43
what is contamination?
when someone gets particles of a radioactive source on their person or inside their body
-> they will continue to be exposed to the radiation until the material has all decayed or is removed
44
what is irradiation?
when someone is exposed to alpha/beta/gamma from a nearby source
-> once the person moves away the irradiation stops
45
dangers of radioactivity
ions in DNA can cause mutations
-> this can result in cell damage and death or cancer
46
what is the relationship between the ionising effect of a radioactive particle and its penetration?
as the ionising power of radiation increases, the penetration power decreases
47
strength of alpha
most ionising
48
weakness of alpha
least penetrating
49
strength of gamma
most penetrating
50
weakness of gamma
least ionising
51
how would you administer alpha (to combat cancer - inside or outside body)
inside -> alpha can't penetrate skin
52
how would you administer gamma (to combat cancer - inside or outside body)
outside -> gamma can penetrate the body
53
what is the relationship between dose or radioactivity and damage to tissue?
the larger the dose, the more damage to tissues
54
how can scientists determine the age of a rock
they can take a sample of the rock and determine the ratio of uranium to lead atoms and use this to work out the age of the rock or how long ago the rock was formed
55
what effect does gamma radiation have on bacterial cells?
it kills and mutates them
56
use of radiation in food?
food is irradiated with gamma radiation to to sterilise it
57
why will food not be 'radioactive' if it's been irradiated with gamma radiation?
the substance has only been exposed to radiation - isn't radioactive
58
why can you irradiate syringes with alpha or beta?
if the needle is made of metal, alpha and beta won't get through
59
uses of radiation in medicine
- kill cancer cells
- medical tracers
60
