7 Radioactivity Flashcards
Alpha particle
- What: 2 protons & 2 neutrons (helium nucleus)
- Charge: +2
- Mass: 4
- Speed: Slow
- Penetration: Paper/Skin
- Ionising: Highly
Beta particle
- What: single electron
- Charge: -1
- Mass: almost none
- Speed: Fast
- Penetration: Thin metal
- Ionising: Mildly
Gamma particle
- What: Electromagnetic wave
- Charge: None
- Mass: None
- Speed: Speed of light
- Penetration: Thick lead (reduced by)
- Ionising: Weak
Alpha decay
A
Initial –>
Z
A - 4
Final +
Z - 2
4
Alpha particle
2
Beta minus decay
A
Initial –>
Z
A
Final +
Z + 1
0
Electron
-1
Beta positive decay
A
Initial –>
Z
A
Final +
Z - 1
0
Positron
1
Gamma decay
- Occurs alongside Alpha or Beta decay
- No change to mass/atomic number
Neutron decay
A
Initial –>
Z
A - 1
Final +
Z
1
Neutron
0
- Non-ionising
- Causes atoms to become radioactive
How to detect radiation
With Geiger−Müller detector
Background radiation
- Small amount of constant radiation that is around us
- Natural sources:
- Cosmic radiation
- Rocks
- Food
- Building materials
- Man-made sources:
- Nuclear bombs
- Nuclear waste
- Medical
Irradiation
- Object exposed to a radiation source, outside the object
- Object doesn’t become radioactive
- Can be blocked
- Stops as soon as the source is removed
Contamination
- Radiation source in/on object
- Object will become radioactive
- Can’t be blocked
- Difficult to remove contamination
Half-life
The average time taken for half of the radioisotopes in a sample to decay.
Radioactivity unit
- Becquerels (Bq)
- The amount of radiation given out by a substance
- One Becquerel = One particle emitted per second
Dangers of radiation
Can ionise atoms in living cells –> can cause mutations (mainly cancer)
Storage and handling of radioactive sources
- Keep in a lead-lined container
- Picked up with tongs
- Use gloves and a mask
- Keep at a safe distance
Photographic film
Becomes fogged when exposed to radiation
Fission
A large element splits into smaller elements. Releases energy as kinetic energy from the products
Fission of U-235
Two daughter, smaller nuclei are produced alongside 3 neutrons
Chain reaction
Uncontrolled nuclear fission
Control rods
- Absorb neutrons to prevent a chain reaction from happening too quickly
- Made from boron
Moderator
- Slows down neutrons
- Made from graphite or water
Nuclear fusion
- Two smaller nuclei fuse into one large nucleus
- High temperature and pressure are needed to overcome intermolecular forces
- Energy source for stars
Smoke detector
- Alpha particles
- If smoke is present, count will decrease, triggering the alarm.
- Alpha particles are stopped by the particles in smoke
Aluminium thickness
- Beta particles
- Count tells thickness
- Used to adjust space between rollers
Tracers
- Gamma
- Radioisotopes are used as tracers to image the body
Treatment
- High radiation doses can be used to kill cells
- Used to treat cancer
Sterilisation
- Gamma
- Gamma radiation can kill bacteria and viruses
- Used to sterilise medical equipment and food
Gamma radiography
- Gamma
- Gamma ray cameras are used to look inside objects
- Airport security
Gauging
- Radioisotopes can be used to measure how much material there’s in a container
Fluid flow
- Radioisotopes can detect traces of sewage or leaks
Radiocarbon dating
Measure Carbon-14 level. It is then compared with the amount of Carbon-14 that would have been present when the sample was part of a living organism.
