4.4.2 - Atoms and Nuclear Radiation
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Atomic Structure
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19 Terms
1
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Why do unstable nuclei give out radiation?
Unstable nuclei undergo decay to become more stable
As they release radiation their stability increases
As they release radiation their stability increases
2
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What is the name of the process in which an unstable nucleus gives out radiation to become more stable?
Radioactive decay
3
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Define the activity of an unstable nucleus.
Activity is the rate of decay of a source of unstable nuclei
4
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What is the unit of radioactive activity?
Becquerel (Bq)
5
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What is count-rate?
The number of radioactive decays per second for a radioactive source
6
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Give an example of a detector that may be used to measure count-rate.
Geiger-Muller tube
7
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State four types of nuclear radiation.
1. Alpha particles
2. Beta particles
3. Gamma rays
4. Neutrons
8
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What are the constituents of an alpha particle?
Two protons and two neutrons
It is the same as a helium nucleus
It is the same as a helium nucleus
9
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What is the range of an alpha particle through air?
A few centimetres (normally in the range of 2-10cm)
10
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What will stop beta radiation from passing through a point?
A thin sheet of aluminium
Several metres of air
Several metres of air
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What will stop gamma radiation from passing through a point?
Several centimetres of lead
A few metres of concrete
A few metres of concrete
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Which type of radiation is most ionising?
Alpha radiation
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Which type of radiation is least ionising?
Gamma radiation
14
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State any changes to mass or charge that occur due to the emission of a gamma ray.
Both mass and charge remain unchanged.
15
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Describe the nature of radioactive decay.
Random
Which nuclei decays and when is determined only by chance
It is impossible to predict which nuclei will decay and when
Which nuclei decays and when is determined only by chance
It is impossible to predict which nuclei will decay and when
16
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Define the half-life of a radioactive isotope.
The time it takes for the number of unstable nuclei in a substance to halve
The time it takes for the count rate from a sample to fall to half its initial level
The time it takes for the count rate from a sample to fall to half its initial level
17
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What is radioactive contamination?
The presence of unwanted radioactive nuclei on other materials
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What is irradiation?
The process of exposing a material to nuclear radiation
The material does not become radioactive
The material does not become radioactive
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Why is it important for the results of studies on the effects of radiation to be published and shared with other scientists?
To allow the findings to be independently checked
This is known as peer review
This is known as peer review
Note 
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