Topic 4 - Nuclear radiation Flashcards
Describe how the model of the atom has changed over time
- 1804 - John Dalton thought each element was made up of a different type of atom
- 1900ish - J.J.Thompson thought atoms were spheres of positive charge with negative electrons throughout (plum pudding)
- 1909 - Rutherford used alpha scattering experiment and found out that most of the mass of the atom must be in nucleus and rest was empty space
- Niels Bohr said electrons orbiting the nucleus do so at certain distances called energy levels
- 1932 - James Chadwick proved the existence of the neutron
Define isotopes
Isotopes of an element are atoms with the same number of protons but a different number of neutrons (mass number is different)
Describe alpha radiation
- when an alpha particle is emitted from the nucleus
- an alpha particle is 2 neutrons and 2 protons (like helium nuclei)
Describe a beta particle
a fast-moving electron released by the nucleus
Describe gamma rays
waves of electromagnetic radiation released by the nucleus
Compare the penetrating power of alpha, beta and gamma radiation
- alpha is stopped by paper/skin (weak)
- beta is stopped by few mm of aluminium (medium)
- gamma is reduced by few cm of lead but never stopped (strong)
Compare the ionising power of alpha, beta and gamma radiation
- alpha is strongly ionising (most)
- beta is weakly ionising (medium)
- gamma is very weakly ionising (least)
Compare the range of radiation in the air of alpha, beta and gamma radiation
- alpha is a few cm (shortest)
- beta is a few metres
- gamma is around a km (longest)
Compare the danger outside of the body of alpha, beta and gamma radiation
- alpha is the least dangerous
- beta is medium
- gamma is the most dangerous
Compare the danger inside of the body of alpha, beta and gamma radiation
- alpha is the most dangerous
- beta is medium
- gamma is the least dangerous
Compare how affected alpha, beta and gamma radiation are by an electric/magnetic field
- alpha is weakly deflected
- beta is strongly deflected
- gamma is not deflected
Define ionisation
when a neutral atom loses or gains an electron (becomes charged)
What happens in alpha decay?
an unstable nucleus emits an alpha particle
What does an alpha decay equation look like?
unstable nucleus –> stable nucleus + alpha particle
(remember the mass and atomic numbers must be equal on both sides)
What happens in beta decay?
a neutron in the nucleus turns into a proton and releases a fast-moving electron
What does a beta decay equation look like?
unstable nucleus –> stable nucleus + beta particle (electron)
(remember the mass and atomic numbers must be equal on both sides)
Define half-life
the time it takes for the number of radioactive nuclei in a sample to halve
What is activity measured in?
Becquerels (Bq)
How do you measure half-life using a graph?
- find half of the count rate
- draw a horizontal line across till it reaches the curve
- draw a vertical line down from the point it reaches the curve (this is 1 half life)
Define background radiation
low-level radiation that’s around us all the time
Define irradation
the process of exposing an object to a source of radiation
Name 2 advantages of irradation
- can be used for sterilisation (removes need for high temps)
- can be used to kill bacteria
Name 2 disadvantages of using irradation
- might not kill all bacteria on an object
- can be very harmful - causes cell damage and mutation
What are ways of protecting yourself from irradation?
- lead-lined boxes
- standing behind barriers
- keeping at a safe distance
Define contamination
process where an object has a radioactive material introduced into it/ on it
Name 2 advantages of using contamination
- radioactive isotopes can be used as medical tracers
- exposure can be limited with the use of isotopes with a short half-life
Name 3 disadvantages of using contamination
- radioactive isotopes may not go where they are wanted
- hard to make sure contamination is fully removed
- can damage healthy cells
What are ways of protecting yourself against contamination?
- using gloves and tongs
- wearing protective suits
What are the main sources of background radiation?
- radon gas from rocks (granite)
- cosmic
- building materials
- air
Define nuclear fission
the splitting of 1 large nucleus to produce 2 smaller ones - 2 or 3 neutrons are also released in the process
Describe how nuclear fission works
- a neutron is absorbed into a nucleus (uranium), causing it to be unstable
- the nucleus splits into 2 daughter nuclei and 2 or 3 neutrons
- the neutrons may collide with another nucleus and cause further fission reactions (chain reaction)
Where does nuclear fusion occur naturally?
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