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Radioactivity Flashcards

1
Q

Why are atomic nuclei unstable?

A

This is because of an imbalance in the forces within the nucleus, as forces exist between the particles in the nucleus

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2
Q

What is an isotope?

A

an atom that has the same number of protons but a different number of neutrons

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3
Q

Why are isotopes unstable?

A

because of their large size or because they have too many or too few neutrons

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4
Q

What do unstable nuclei emit to become more stable?

A

Radiation

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5
Q

What can radiation be in the form of?

A

a high energy particle or wave

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6
Q

What happens as the radiation moves away from the nucleus?

A

it takes some energy with it
This reduces the overall energy of the nucleus
This makes the nucleus more stable

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7
Q

What is the process of emitting radiation called?

A

Radioactive decay

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8
Q

What type of process is radioactive decay?

A

a random process

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9
Q

Why is radioactive decay a random process?

A

As it is not possible to know exactly when a particular nucleus will decay

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10
Q

What device is used to detect radiation?

A

A Geiger-Muller tube

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11
Q

What happens within the Geiger-Muller tube?

A

ions are created by radiation passing through it

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12
Q

Why is the Geiger-Muller tube connected to a Geiger counter?

A

The Geiger counter counts the ions created in the Geiger-Muller tube

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13
Q

What is count-rate?

A

Count-rate is the number of decays recorded each second by a detector

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14
Q

What are objects containing radioactive nuclei called?

A

Sources of radiation

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15
Q

What is activity?

A

The rate at which the unstable nuclei from a source of radiation decays

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16
Q

What is the equation for activity?

A

Activity (Bq) × Time period (s)

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17
Q

What is the equation for count rate?

A

Number of decays ÷ Time period (s) = … decays per second

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18
Q

What kind of radiation is emitted by an unstable nucleus?

A

nuclear radiation

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19
Q

Why is an alpha particle the same as a helium nucleus

A

This is because they consist of two neutrons and two protons

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20
Q

What charge do alpha particles have?

A

+2

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21
Q

What can alpha particles be affected by?

A

an electric field as they have a charge of +2

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22
Q

What are beta particles?

A

they are fast-moving electrons

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23
Q

Where are beta particles produced?

A

They are produced in nuclei when a neutron changes into a proton and an electron

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24
Q

What do beta particles have a charge of?

A

-1

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25
What can beta particles be affected by?
an electric field as they have a charge of -1
26
What are gamma rays?
electromagnetic waves | that have no mass and no charge
27
How do gamma rays differ from other electromagnetic waves?
they have the highest energy
28
What do gamma rays not have?
a charge
29
Why are neutrons neutral?
they have no charge
30
What are the properties of alpha particles?
Range in air: few cm Penetration: stopped by paper Ionisation: high
31
What are the properties of beta particles?
Range in air: few 10s of cm Penetration: Stopped by a few mm of Aluminium Ionisation: medium
32
What are the properties of gamma rays?
Range in air: infinite Penetration: reduced by a few mm of Lead Ionisation: low
33
What is all nuclear radiation capable of?
ionising atoms that it hits
34
What happens when an atom is ionised?
the number of electrons it has changes | which gives it a non-zero charge
35
What are the uses of radiation?
For: Producing electricity through nuclear fission Medical procedures including diagnosis and treatment Testing material Determining the age of ancient artefacts Checking the thickness of materials Smoke detectors
36
What is nuclear fusion?
fusion of light nuclei to form heavier nuclei release a lot of energy happens in stars as it requires high temperatures and pressures how all elements heavier than hydrogen were made
37
Why does nuclear fusion produce a lot of energy?
some of the mass of the original nuclei is converted into energy
38
What is nuclear fission?
When a fired neutron is absorbed by a large nucleus and splits a large unstable nucleus into 2 smaller nuclei and 2 or 3 neutrons creates a chain reaction smaller nuclei are called daughter nuclei used in nuclear reactors
39
How can nuclear fission be controlled?
using control rods that are inserted into the reactor | and absorb neutrons
40
What is the energy released from nuclear reactors used for?
to heat water and turn it into steam which can turn turbines to generate electricity in a electricity generator
41
What are the pros and cons of nuclear energy?
Pros: uranium and plutonium are cheap (and provide a large amount of energy) cleaner (doesn't produce greenhouse gases) Cons: power plants are expensive to set up nuclear waste is expensive to get rid off chance of disasters
42
What is irradiation?
the process by which objects are exposed to radiation
43
What are the types of ionising radiations?
Alpha Beta Gamma X-rays
44
What are the types of non-ionising radiation?
ultraviolet | microwaves
45
What is contamination?
When radioactive particles get onto other objects
46
What is the problem with contamination?
Radioactive particles are likely to decay and irradiate you
47
What determines how harmful radiation is?
what type of radiation it is location (inside, outside or on the body) Dosage (how long you have been exposed, how far away from the source you are, how radioactive the substance is)
48
When does the emission of a neutron occur?
When an unstable nucleus (has too many neutrons) loses a neutron in order to become stable
49
Why is ionising radiation more harmful?
It can enter living cells and interact with molecules inside it can ionise our DNA - causing mutations which could lead to cells diving uncontrollably - causing cancer
50
What are the safety measures to protect against radiation?
wear gloves and overalls hold with tongs place substance in a lead-lined box
51
What are the symptoms of radiation sickness?
hair loss vomiting tiredness
52
What are the methods of radiotherapy?
Externally: gamma rays fired at the tumour (so it receives the highest dose) Internally: a radioactive source is either placed inside cancer cells or next to cancer cells which fires beta radiation
53
What is radiotherapy used for?
to treat cancer
54
What are medical tracers used for?
to track the movement of isotopes around the body (by tracking the radiation they emit) which can be used to check if organs are working properly
55
How are medical tracers inserted into the body?
by injecting or swallowing it
56
What isotopes are used for medical tracers?
isotopes with a short half-life as they emit radiation for a short period which stops them from being harmful
57
What are the benefits and risks of radiation?
Medical tracer: can identify and diagnose diseases but requires low doses and a short half-life Radiotherapy: can save a life so worth the side-effects may only prolong a person's life
58
1 Bq (Becquerels) =
1 decay per second
59
What is half life?
The time taken for the number of radioactive nuclei in a sample to halve which causes the number of decays/activity to also halve (decrease)
60
Alpha decay equation
e.g. 226 4 Ra ---> x + He 88 2
61
Beta decay equation
e.g. 14 14 0 C ----> N + e 6 7 -1
62
Gamma equation
... ---> .... + y (gamma symbol)
63
What is the relative atomic mass of an electron?
1/2000 (very small)
64
What happens when the shells increase?
their energy levels increase
65
What is ionisation?
when electrons absorb enough energy to leave their atom | which leaves behind a positive ion - more protons than electrons
65
What is ionisation?
when electrons absorb enough energy to leave their atom | which leaves behind a positive ion - more protons than electrons
66
What did John Dalton describe atoms as?
solid spheres | different types of spheres make up different elements
67
What did J.J Thompson describe the atom as?
A plum pudding | the atom is a ball of positive charge that consists of negatively charged electrons
68
What was Rutherford's experiment?
Rutherford shot a beam of positively charged particles (alpha particles) at a thin sheet of gold foil
69
What were the expected results in Rutherford's experiment?
He expected the particles to pass through the foil because the positive charge of the nucleus was thought to be evenly spread out.
70
What does the nuclear model describe the atom as?
Nearly all of the mass of the atom is concentrated in the centre of the atom (in the nucleus) The nucleus is positively charged Negatively charged electrons orbit the nucleus at a distance
71
What did Niels Bohr suggest?
Electrons orbit the nucleus in fixed shells at set distances from the nucleus
72
What prevents the atom from collapsing?
the orbiting of the electrons
73
What did James Chadwick discover?
the neutron | which have no charge and the same mass as a proton
74
What happens when atoms absorb electromagnetic radiation?
electrons move to a higher energy level further away from the nucleus
75
What happens when atoms emit electromagnetic radiation
electrons drop to a lower energy level closer to the nucleus
76
How does photographic film detect radiation?
a bright spot appears where ionising radiation hits the film
77
How does a smoke detector work?
A radioactive material fires alpha particles at a smoke detector. If there is smoke between the radioactive material and the smoke detector, then fewer alpha particles will reach the detector. This will set off the smoke alarm.
78
How is radiation used in paper production?
We can fire beta particles through paper in a factory to make sure that the paper being produced is the right thickness. If the thickness of the paper changes, greater or fewer beta particles will reach the detector. Production can then be stopped.
79
What is background radiation?
the radiation that we are exposed to all around us everyday

Physics (9 decks)

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