GCSE Physics > Topic 4 - Atomic structure > Flashcards

Topic 4 - Atomic structure Flashcards

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1
Q

DEVELOPING THE MODEL OF THE ATOM:
What changes could new experimental evidence lead to?

A

a scientific model being changes or replaced

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2
Q

DEVELOPING THE MODEL OF THE ATOM:
What were atoms thought to be like before the discovery of the electron?

A

tiny spheres that could not be divided

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3
Q

DEVELOPING THE MODEL OF THE ATOM:
IN what order were the subatomic particles discovered?

A
  • electron
  • proton
  • neutron
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4
Q

DEVELOPING THE MODEL OF THE ATOM:
What model did the discovery of the electron lead to?

A

the plum pudding model

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5
Q

DEVELOPING THE MODEL OF THE ATOM:
Describe the plum pudding model?

A
  • a ball of positive charge
  • negative electrons embedded in it
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6
Q

DEVELOPING THE MODEL OF THE ATOM:
What did the results of the alpha particle scattering experiment lead to?

A
  • the conclusion that the mass of an atom was concentrated at the centre (nucleus)
  • the nucleus was charged
  • this nuclear model replaced the plum pudding model
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7
Q

DEVELOPING THE MODEL OF THE ATOM:
How did Niels Bohr adapt the nuclear model?

A
  • suggesting that the electrons orbit the nucleus at specific distances (energy levels)
  • his theoretical calculations agreed with experimental observations
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8
Q

DEVELOPING THE MODEL OF THE ATOM:
How were protons discovered?

A

later experiments lead to the idea that the positive charge of any nucleus could be subdivided into a whole number of smaller particles, each particle having the same amount of positive charge
- these particles were called protons

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9
Q

DEVELOPING THE MODEL OF THE ATOM:
The experimental work of which scientist proved the existence of neutrons within the nucleus?

A

James Chadwick

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10
Q

DEVELOPING THE MODEL OF THE ATOM:
How long after the idea of the nucleus was accepted was the existence of neutrons proven?

A

about 20 years

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11
Q

DEVELOPING THE MODEL OF THE ATOM:
How did the evidence from the scattering experimant lead to a change in the model?

A
  • they expected the alpha particles to pass straght throgh the gold foil or only be slightly deflected
  • some were deflected more than expected and others backwards
  • this made them realise that there must be a mass at the center with a positive charge (as it repelled the positive alpha particles)
  • as most of the particles wnet straight through, they also realised most of the atom was empty space
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12
Q

DEVELOPING THE MODEL OF THE ATOM:
What are the main differences between the plum pudding and the nuclear model?

A
  • most of the nuclear model id empty space, when most of the plum pudding is a sphere of positive charge
  • ## the positive charge is concentrated in the center of the nuclear model but the plum pudding is a ball of positive charge
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13
Q

HALF LIFE:
What will radioactive substances always do?

A

give out radiation from the nuclei of their atoms

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14
Q

HALF LIFE:
How can this radiation be measured?

A
  • with a geiger-muller tube and counter
  • records the count rate
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15
Q

HALF LIFE:
What is the count rate recoded by a geiger-muller tube?

A

the number of radiation counts reaching it per second

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16
Q

HALF LIFE:
Why can’t you predict when or which nucleus in a sample will decay next?

A

radioactive decay is entirely random

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17
Q

What is radioactive decay?

A

when unstable isotopes decay into other elements and give out radiation as they try to become more stable

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18
Q

HALF LIFE:
What is half life?

A

the time it takes for the amount of radiation emitted by a source to halve

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19
Q

HALF LIFE:
What can we use to make predictions about radioactive substances, even though the decays are random?

A

Half-life

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20
Q

HALF LIFE:
What can half-life be used to find?
What are the units?

A
  • the rate at which a source decays (its activity)
    becquerels, Bq (1 Bq +1 decay per second)
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21
Q

HALF LIFE:
What is the activity of a radioactive substance?

A

the rate at which a source decays

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22
Q

HALF LIFE:
What happens to the activity every time a radioactive nucleus deacys to mecome stable?

A

the activity as a whole will decrease
(older sources emit less radiation)

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23
Q

HALF LIFE:
Why do we have to use HALF-life to measure how quickly the activity drops off?

A

the activity never reaches 0

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24
Q

HALF LIFE:
What is the definition of half-life?

A

the time taken for the number of radioactive nuclei in an isotope to halve
(also for the activity and count rate to halve0

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25
HALF LIFE: What happen to the activity in materials with a short half-life, explain why?
- activity falls quickly - nuclei are very unstable and decay rapidly
26
HALF LIFE: Why are sources with a short half-life dangerous?
- they emit a high amount of radiation at the start, but they quickly become safe
27
HALF LIFE: What happens to the activity in materials which have a long half life? Why?
- activity falls more slowly - most of the nuclei don't decay for a long time 9the source just sits there, releasing small amounts of radiation of a long time)
28
HALF LIFE: Why are substances with a long half-life dangerous?
nearby areas are exposed to radiation for (millions of) years
29
BACKROUND RADIATION + CONTAMINATION: What is backround radiation?
the low level backround radiation that is around us all the time
30
BACKROUND RADIATION + CONTAMINATION: What do you need to do with backround radiation in calculations?
measure and substract the backround radiation from you results to aviod systematic errors
31
BACKROUND RADIATION + CONTAMINATION: Name the 3 places backround radiation comes from?
1) radiactivity of naturally occuring unstable isotopes 2) Radiation from space (cosmic rays) 3) Radiation due to human activity (tiny proportion)
32
BACKROUND RADIATION + CONTAMINATION: Where could naturally occuring unstable isotopes be found?
- air - food - building materials - rocks under our feet
33
BACKROUND RADIATION + CONTAMINATION: Where does most of the radiation from space come from, how are we peotected from this?
- mostlycompes from the sun - the earth's atmosphere protects us from most of this radiation
34
BACKROUND RADIATION + CONTAMINATION: Where could radiation from human activity come from?
fallout from nuclear explosions or nuclear waste
35
BACKROUND RADIATION + CONTAMINATION: What does radiation dose tell you?
the risk of harm to body tissues due to exposure to radiation
36
BACKROUND RADIATION + CONTAMINATION: What units is radiation dose measured in?
sieverts (Sv)
37
BACKROUND RADIATION + CONTAMINATION: What is the dose of backround radiation measured in,why/
millisieverts - the dose from backround radiation is small (1Sn + 1000mSv)
38
BACKROUND RADIATION + CONTAMINATION: What two factor can affect your radiation dose?
- where you live - if you have a job that involves radiation
39
BACKROUND RADIATION + CONTAMINATION: What is exposure to radiation called?
irradation
40
BACKROUND RADIATION + CONTAMINATION: What happens to an object near a radioctive source?
it gets irradated by it - it's exposed to it (we are always being irridated by backround radiation sources)
41
BACKROUND RADIATION + CONTAMINATION: True or False: Irradating something makes it radioactive
False
42
BACKROUND RADIATION + CONTAMINATION: State 4 ways to reduce the ffects of irradation
- keeping sources in lead-lined boxes - standing behind barriers - being in a different room - using remote-controlled arms
43
BACKROUND RADIATION + CONTAMINATION: What is contamination?
when radioactive particles get onto objects
44
BACKROUND RADIATION + CONTAMINATION: When is an object said to be contaminated?
if unwanted radioactive atoms get onto or into an object
45
BACKROUND RADIATION + CONTAMINATION: Explain why contamination is dangerous?
the contaminating atoms can then decay, releasing radiation which could cause you harm (contamination is especially dangerous because radioactive particles could get inside your body)
46
BACKROUND RADIATION + CONTAMINATION: Name 2 ways to avoid contamination?
- gloves and tongs used when handling sources, avoids getting particles stuck to your skin or under your nails - industrail workers might wear protective suits to stop them breathing in particles
47
BACKROUND RADIATION + CONTAMINATION: Which radiation sources are most dangerous outside the body?
beta and gamma - high levels of irridation are dangerous from all sources, but particilary from those which emit beta and gamma
48
BACKROUND RADIATION + CONTAMINATION: Why are beta and gamma sources the most dangerous outside the body/
they can penetrate the body and get to the delicate organs
49
BACKROUND RADIATION + CONTAMINATION: Why is alpha less dangerous outside the body?
it can't penetrate the skin and is easily blocked by a small air gap
50
BACKROUND RADIATION + CONTAMINATION: Which radiation source is the most dangerous inside the body?
alpha
51
BACKROUND RADIATION + CONTAMINATION: Why is alpha the most dangerous inside the body/
alpha sources do all their damage in a very localised area
52
BACKROUND RADIATION + CONTAMINATION: What is the main concern when working with alpha sources?
contamination, rather than irradation - alpha sources do all their damage in a very localised area
53
BACKROUND RADIATION + CONTAMINATION: Why are beta sources less damaging in the body?
radiation is absorbes over a wider area, and some passes out of the body altogether
54
BACKROUND RADIATION + CONTAMINATION: Which radiation source is the least damaging inside the body and why?
- gamma - they mostly pass straight out - they have the lowest ionising power
55
BACKROUND RADIATION + CONTAMINATION: Why is it important we understand how radiation affects our bodies?
we can better protect ourselves when using it
56
USES AND RISK: What can happen if radiation enter living cells?
it can ionise atoms and molecules within them - this can lead to tissue damage
57
USES AND RISK: What is the danger with lower doses of radiation?
tends to cause minor damage without killing the cells this can give rise to mutant cells which divide uncontrollably - this is cancer
58
USES AND RISK: What is the danger with higher sources of radiation?
tends to kill cells completely this causes radiation sickness (leading to vomiting, tiredness and sickness) if a lot of cells all get blatted at once
59
USES AND RISK: Name 2 uses of gamma radiation?
- medical tracers - radiotherapy
60
USES AND RISK: How can gamma sources be used as medical tracers?
certain radioactive isotopes can be injected into people (or swallowed) and their progress around the bosy is followed using an external detector a computer converts the reading to a display showing where the strongest reading is comping from
61
USES AND RISK: Give an example of an isotope that can be used as a medical tracer. Explain how it is used.
the use of iodine-123 absorbes by the thyroid glanf like normal iodine-127, but it gives out radiation which which can be detected to indicate whether the thyroid gland if taking in iodive as it should
62
USES AND RISK: What type of isotope is used in medical tracers? Why?
gamma (never alpha) - the radiation passes through the body without causing too much ionisation
63
USES AND RISK: What other property should the isotopes used in medical tracers have?
they should have a short half-life so radioactivity inside the patient quickly dissapears
64
USES AND RISK: What is radiotherapy?
treating cancer with radiation
65
USES AND RISK: Why can high doses of ionising radiation be used to treat cancers?
it will kill all living cells
66
USES AND RISK: How does radiotherapy work?
- gamma rays are carefully directed at just the right dosage to kill the cancer cells without damaging too many normal cells - radiation emitting implants (usually beta-emitters) can also be put next to or inside tumours
67
USES AND RISK: What are the main disadvantages to radiotherapy?
- lots of damage to normal cells, this makes the patient feel very ill - but if the cancer is killed off in the end, it's worth it
68
USES AND RISK: What are the risks and benefits of using a tracer?
- can diagnose life-threatening conditions - risk of cancer from one use is small
69
USES AND RISK: Why do many cancer patents still choose to have radiotherapy?
- it can get rid of their cancer entirely - proplonged exposure to radiation poses future risks and side-effects - but for them, benefits outweigh the risks
70
USES AND RISK: What is perceived risk?
- how risky someone thinks something is (not actual risk) - this can vary from person to person
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