Atomic structure Flashcards
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What are two common isotopes that are used in nuclear fission and why are they used instead of other elements (3)
- Plutonium 239
- Uranium 235
- They are used instead of other elements because they are massive and unstable so can be easily used to start a chain reaction.
The fission process explained (5)
- In fission, the bonds that hold the nucleus together are
broken and thermal energy is released. - The remaining parts of the original nucleus form two
daughter nuclei and some individual neutrons.
-When the individual neutrons collide with other
unstable nuclei they are likely to go through the same
process.
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- This can lead to a chain reaction of more
neutrons colliding with other unstable nuclei and the
process repeating.
- While producing more and more
energy.
What happens if the chain reaction of nuclear fission is not controlled (1)
- A nuclear explosion will go off
How do nuclear reactors control this reaction (2)
Supply an example of materiel
They use control rods that can be made from a variety of elements such as (indium, silver, or cadmium) to absorb stray neutrons.
Nuclei with too many or too few neutrons do exist but are unstable and will do what
decay by emitting radiation
What happens to an atom as the number of protons increases what is required if the number of protons increases and why
more neutrons are required to keep the nucleus stable
Alpha particle
two protons and two neutrons
Alpha decay causes what to the mass number and atomic number
To decrease by 4 and the atomic number of the nucleus to decrease by 2
How is a beta particle produced and what is it
If the nucleus has too many neutrons, a neutron will turn into a proton and emit a fast moving electron. This electron is called a beta particle. This process is known as beta radiation
Electrons are not normally expected to be found in the nucleus but neutrons can split into a positive proton.
What happens next
An electron which has negative charge to balance the positive charge is then ejected at high speed and carries away a lot of energy
Beta decay causes the atomic number of the nuclues to …
and the mass number to ..
atomic number increase by 1 and mass number is the same
After emitting an alpha or beta particle, the nucleus will often still be too “hot”. How does the nucleus lose energy
The nucleus will cool down by emitting a more energetic electromagnetic wave called a gamma ray
When can a neutron be emitted by radioactive decay
This can occur naturally, ie absorption of cosmic rays high up in the atmosphere can result in neutron emission.
Neutron emission causes the mass number to decrease/increase/stay the same by x
atomic number to decrease/increase/stay the same by x
Mass number decrease by one and atomic number remain the same
Alpha properties
Penetrating power: Skin/paper
Ionising power: high
Range in air: 5 cm
Beta properties
Penetrating power: stopped by thin sheet of aluminum
ionising power: low
range in air: 1 meter
Gamma properties
Penetrating power: 1 meter of concrete
Ionising power: very low
Range in air: 1 kilometer
How do the Geiger Muller tube, or the G-M tube generally work
The radiation ionise the gas inside and resulting charged particles move across the chamber and get counted as charges rather like an ammeter
Why does gamma not change the structure of a particle
It is pure energy
Nuclear fuel in reactor
The uranium isotope that will split when triggered by an incoming neutron the fuel is held in rods so that the neutrons will fly out and cause nuclear fission in other rods.
Graphite core in reactor
graphite slows the neutrons down so that they are more likely to be absorbed into a nearby fuel rod.
Control rods
These are raised and lowered to stop neutrons from travelling between fuel rods and therefore change the speed of the chain reaction
Coolant
This is heated up by the energy released from the fission reactions and used to boil water to drive turbines in the power station
