P6- Radioactivity Flashcards
What is an isotope
An atom with a different number of neutrons
What happens to unstable isotopes
They undergo radioactive decay
Define a radioactive material
A material that consists of unstable isotopes that can decay
What are the 3 types of radiation
- Alpha
- Beta
- Gamma
What is an alpha particle
A helium nucleus
- 2 protons
- 2 neutrons
What is the charge of an alpha particle
2+
(they have no electrons)
How is an alpha particle writen
4
He
2
How far can alpha particles travel
A few cm in air
What can absourb alpha radiation and why
A piece of paper.
Because alpha particles are relatively large.
How ionising is alpha radiation
Strongly ionising
- large 2+ charge
- can knock electrons off atoms easily
What is a beta particle
An electron
How do you write a beta particle
0
e
-1
How is beta radiation emitted
An atoms neutron decays into a proton and an electron, the electron is emitted at high speeds from the nucleus.
How ionising is beta radiation
Moderately ionising
- 1- weaker charge
- cannot knock electrons easily
How far can beta radiation travel
Several meters of air
What can stop beta radiation
5mm of aluminium
What is gamma radiation
Waves of electromagnetic radiation often emitted after alpha or beta radiation to remove extra energy
What is nuclear fusion
Nuclear fusion is the fusing of two lighter nuclei to make a single heavier nucleus and a lot of energy is emitted in the form of electromagnetic radiation.
Is mass always conserved
No mass is not always conserved. It is not in nuclear fusion
What causes the release of engery in nuclear fusion
Some of the mass from the 2 starting nuclei is converted into large amounts of engery
What are the benifits of nuclear fusion
- No nuclear waste
- Hydrogen fuel is easily available
What circumstances must occour for nuclear fusion to happen
Extremely high tempuratures and pressure
In nuclear fusion what form is energy released
Electromagnetic radiation
What eqaution is used to work out energy released in nucear fusion
E=m x c^2
Where does nuclear fusion comenly occour
In stars. Mostly hydren nuclei fusing to produce Helium
What is nuclear fission
When a large unstable nucleus absourbed a neutron and splits into 2. This releases Engery and usually neutrons
What is the process of Nuclear fission and the chain reaction that can occour
- A neutron hits a nucleus
- This makes the nucleus unstable so it decays
- It decays into 2 smaller nuclei, some neutrons and engery
- The realsed neutrons can then hit other nuclei and cause them to decay
- This causes the chain reaction
How can you limit the amount of energy produced in nuclear fission
By slowing down or absourbing the neutrons you can control the amount of energy prodcued and the length of the chain reaction
What is used in nuclear reactors to control nuclear fission
- Control rods which absourb excess neutrons (boron)
- Moderators to slow down the neutrons usually water or graphite
What is activity
(refering to isotopes)
The overal rate of decay in a group of radioactive decay
What is decay mesured in
Becquerels
1 Bq = 1 decay per second
Define Half lives
The time taken for the number of radioative nuclei to halve
OR
The time taken for the activity to halve.
Both definintions are perfectly corrolated
How do you determine the half life of a material from a graph
Across where the activity has halved and down to the time it takes for one half life to occour
