Atomic Structure Flashcards
What is activity?
The rate at which an unstable nucleus decays. This is in all directions.
What is count rate?
The number of decays per second. This measures activity in one direction.
What is used to measure radiation?
A Geiger Muller tube.
What is the largest source of background radiation?
Radon gas.
What is background radiation?
The radiation that is around us all the time.
What are some natural sources of background radiation?
- Radon gas
- Cosmic rays
What are some man made sources of background radiation?
Medical.
What happens when an atom absorbs EM radiation, and what is this process called?
Excitation
An electron moves further from the nucleus.
How is electro-magnetic radiation emitted?
De-excitation
An electron moves closer to the nucleus.
What is alpha radiation?
A helium nucleus.
2 neutrons and 2 protons.
What is beta radiation?
A high energy electron.
What is gamma radiation?
An Em wave.
What makes an atom radioactive?
Too many protons or neutrons, which make the nucleus unstable.
Where in the atom are all types of radiation emitted from?
The nucleus.
What is the charge of alpha radiation?
+2
How far can alpha radiation travel in air?
5cm
What is alpha radiation absorbed by?
Paper
How ionising is alpha radiation?
Strongly ionising.
What is beta radiation absorbed by?
Aluminium.
How far can beta radiation travel in air?
1m
How ionising is beta radiation?
Weakly ionising.
What is gamma radiation reduced by?
- cm’s of lead
- m’s of concrete
How far can gamma radiation travel in air?
Unlimited range.
Why are alpha particles the most ionising?
They are the largest.
What is neutron emission?
A free neutron.
What causes neutron emission?
Spontaneous or induced nuclear fission.
How far can neutron radiation travel in air?
1000’s of m’s
What blocks neutron radiation?
Hydrogen rich materials
- Water
- Concrete
How can neutron emission be ionising?
By making other atoms unstable and radioactive.
What happens to an atom when it emits an alpha particle?
- Mass number decreases by 4
- Atomic number decreases by 2
- It changes into a new element
What happens to an atom when it emits an beta particle?
- Mass number remains the same
- Atomic number increases by 1
- It changes into a new element
Where does the beta particle come from?
A neutron turns into a proton and an electron, the proton remains in the nucleus and the electron is emited.
What is half life?
Time for half the nuclei to decay
OR
Time for the count rate to half
Which isotope is used for carbon dating?
Carbon 14.
How does carbon 14 end up in plants and animals?
- It combines with oxygen to form radioactive carbon dioxide
- Absorbed by plants for photosynthesis
- Plants are then eaten by animals
Why does the amount of carbon 14 decreases once an organism has died?
It stops exchanging carbon with its atmosphere, and the carbon 14 starts to decay.
What is contamination?
Where radioactive atoms get onto materials where they are not wanted.
What is irradiation?
When an object is exposed to nuclear radiation.
Which type of radiation is used for irradiating food?
Gamma.
What is irradiation used for?
- Making food last longer
- Sterilising medical equipment
Why is irradiating used for some medical equipment insted of heat sterilisation?
High temperatures could melt/damage some components.
What are some uses of radiation, and what type of radiation does each use?
- Smoke detectors (alpha)
- Thickness control (beta)
- Sterilising (gamma)
- Medical tracers (gamma)
- Industrial tracers(gamma)
What property of gamma radiation makes in appropriate for use in radiotheripy?
It can be focused to a point.
Why do people wear protective clothing when handling radioactive material?
It prevents contamination.
How is radiation used in medicine?
- Tracers (show flow through an organ)
- Gamma camera (gamma injected into the body and detected)
- Radiotherapy
- Implants (Destroying cancer cells)
When is alpha radiation dangerous?
When it is inside the body.
How do people who work with radiation reduce the risk?
- Distance from the source
- Short time near the radiation
- Using shielding
What is released when a large nucleus splits in nuclear fission?
- Smaller daughter nuclei
- More neutrons
- Energy
- Gamma rays
Why do the masses of the of the products of nuclear fission not add up the the mass of the original nuclei?
Some mass is converted to energy.
How does a nuclear power station generate electricity?
Heat from the reactor is used to boil water, this steam then turns a turbine which turns a generator.
What do the fuel rods contain?
Enriched uranium
What is enriched uranium?
Uranium which contains a higher percentage of uranium-235 that the natural ore.
What do the control rods do?
They absorb neutrons, and can be moved in and out to control the speed and temperature of the reaction.
What are the control rods made from?
Boron/Cadmium
What does the moderator do?
Slows down neutron to allow them to be absorbed by the uranium nuclei.
What is the moderator made from?
Graphite or water.
What does the coolant do?
Water flows around the reactor and transfers thermal energy way from it. This can also act as the moderator.
Why does the fuel need to be extremely hot for nuclear fusion?
It has to be made into plasma.
Why does the fuel for nuclear fusion need to be plasma?
So that the particles can collide without rebounding due to electrostatic repulsion.
What is a plasma?
A gas where the electrons have been stripped from the nuclei.
Does fission or fusion release more energy per kg of fuel?
Fusion.
What is the fuel for nuclear fusion?
Isotopes of hydrogen which can be made from water and lithium.
Which isotopes of hydrogen are used for nuclear fusion?
Deuterium and tritium
What condition is neaded for nuclear fusion other than temperature?
High pressure
Where does the energy for nuclear fusion come from?
Mass is converted into energy.
