Flashcards in 6 Deck (36)
Scale of an atom:
If a golf ball was a proton the space in a atom is 1 mile.
Nucleus of a atom is:
Number of protons =
RAM - atomic number.
What is an isotope?
A atom with a different number of neutrons.
A different mass number but the same atomic number.
Sent atoms to hit a very thin wall of gold foil. He measured how many bounced off and how many went straight through. This is due to atoms being mostly empty space.
- when a electron Gaines energy and jump to the next electron shell.
- when a electron is exited and is on a higher electron shell that it should this occurs.
- the electron drops down a shell to its original place.
- this releases energy.
- this is how neon gives out light.
What is another name for an electron shell?
What instrument measures radiation.
Sources of background radiation:
- the ground
- man-made radiation
- cosmic radiation
- radon gas.
- made from helium nucleus
- RAM of 4
- charge of +2
- highly ionising
- stopped by paper
- made from high energy or free electron.
- RAM of 0 or 1/1836
- charge of -1
- reasonably ionising.
- stopped by tin foil.
- made from free electron but with operative charge.
- RAM 0 or 1/1836
- charge of +1
- made from high frequency energy waves.
- RAM is 0
- charge is neural
- low ionising ability
- very long range only lead can stop it.
Radio active decay for alpha.
- 4 off RAM
-2 off atomic number.
Radio active decay for beta
- nothing happens to RAM
+1 to atomic number
A neutron turns into a proton and a electron is created and emitted.
Radio active decay for positron.
- nothing to RAM
-1 to atomic number.
A proton turns to a neutron, positron is then emitted.
Unit of half life is:
When does a radioactive isotope decay?
Half life is:
- the time it takes for the nucleus to halve in size.
What are alpha particles used for?
- highly ionising things
- smoke detectors.
- thickness in paper
What are beta particles used for?
- gauging thickness with rollers - tin foil.
- 1m range in air
What are gamma rays used for?
- irradiating food
- sterilises equipment
- treats cancer
- kind of PET scan.
What happens in PET scans?
- positrons emitted into the patients body. These then come into contact with a electron and they annihilate each other and gamma rays are produced and they when the leave the body they are detected. These are used to form an image.
Radiation can either cause:
- if exposed to a lot - kills cell directly
- if only exposed to a little it can cause cancer
- and radiation poisoning.
What is radiotherapy ?
Where external source of a gamma ray emitter fires the gamma rays into the body in an attempt to kill cancer cells.
Or put in an internal source of a beta emitter near the tumour to kill the cells that way.
What is a medicinal tracer?
- a gamma emitter is put into the body.
- this can then be tracked to see if the body is working as it should.
- This gamma emitter has a very short half life.
What is nuclear fission?
- happens in nuclear power plants.
- where uranium atoms are split by neutrons being fired at there nucleus.
- when this happens 3 more neutrons are released so the chain reaction takes place.
What is a moderator?
- slows down the speed of neutrons in nuclear fission so that the uranium nuclei can absorb them.
- helps it react.
- often made of graphite.