P1 Atomic Structure Flashcards
What do you call nuclei that give out radiation?
Unstable nuclei
Define the activity of a radioactive source.
The rate at which it decays
What is the activity measured in?
becquerels (Bq)
What is one becquerel equivalent to?
One decay per second
What material stops alpha radiation?
A few centimetres of air or paper
Alpha is lowly penetrating and highly ionising
What material stops beta radiation?
A few milimetres of aluminium
Beta is medium penetrating and medium ionsising.
What material stops gamma radiation?
Many centimetres of lead or metres of concrete
Gamma is highly penetrating and lowly ionsising.
What is a gamma particle made up of?
Electromagnetic radiation
What is an alpha particle made up of?
Two neutrons and two protons (a helium nucleus)
What is a beta particle made up of?
A high-speed electron from where a neutron has turned into a proton.
What is the fourth type of nuclear radiation?
A neutron (n)
Define Radioactive contamination.
The unwanted presence of radioactive material on another object/thing and it becomes radioactive.
What is irradiation?
The process of exposing an object to nuclear radiation where it doesn’t become radioactive itself.
Name 3 different ways to protect against unwanted irradiation.
- using sources of the lowest activity possible
- wearing protective clothing
- not handling sources with bare hands
What is the half-life of a radioactive isotope?
The average time it takes for half the nuclei to decay / time for the count rate to fall to 50% of its original value.
Define count rate.
The number of decay recorded each second by a detector.
Name 2 facts about isotopes with a short half-life.
- They are very unstable, so exposure can be very hazardous
- They do not remain radioactive for long
Name 2 facts about isotopes with a long half-life.
- They are more stable, so they aren’t radioactive for long
- Exposure is less hazardous as radiation is emitted very slowly.
How is nuclear radiation used in medical tracers?
- The radioactive isotope is ingested or injected into the body.
- It can be detected outside of the body due to the high penetration power.
Name 2 specific uses of radioactive isotopes used as medical tracers.
- To monitor kidney function: if it builds up in a kidney it could indicate that one isn’t functioning efficiently.
- To locate damage or blockages in intestines: radioactivity can’t be detected if there’s a blockage, and if there’s damage to the intestines, it passes out into other areas of the body.
What must be considered when choosing which isotope to use for a specific job?
The half-life, penetration power, and how ionising it is.
e.g. medical uses require something with a short half-life and low ionising power, but a smoke detector would require something with a longer half-life and high ionising, but lowly penetrating.
What must be done to properly evaluate any new risks from new studies?
It must be peer reviewed and tested through experiment to prove that the results are reproducible.
What factors affect the level of background radiation that somebody experiences?
Their location and occupation
What percentage of radiation is from natural sources?
87%
(includes from: radon gas, food, gamma rays, and cosmic rays)
Define nuclear fission.
The splitting of a large unstable nucleus through absorbing a neutron.
What is emitted as a result of nuclear fission?
- 2 smaller nuclei of roughly equal size
- 2 or 3 neutrons
- gamma rays
- energy
How does the chain reaction form?
All of the products have kinetic energy so they move and get absorbed by other large unstable nuclei, creating a chain reaction.
What is this chain reaction like in a nuclear reactor?
It is controlled to give a constant, steady release of energy, they use graphite rods to absorb the unwanted neutrons.
What is the chain reaction like in nuclear weapons?
Nuclear weapons are the result of uncontrolled chain reactions
Define nuclear fusion.
The joining of two smaller nuclei to form a larger nucleus.
What is emitted from nuclear fusion?
- Some of the mass is converted into energy
- Some of the energy can be emitted as radiation
What conditions must be met for nuclear fusion?
Very high temperatures and pressures to overcome the electrostatic repulsion so that the positive nuclei can be close enough for fusion to take place.
What particle is represented by He^4,2?
Alpha
What particle is represented by e^0,-1
Beta
How much do each of the radiation particles reduce the mass number by if emitted?
alpha = -4
beta = 0
gamma = 0
How much do each of the radiation particle reduce the atomic number by if emitted?
Alpha = -2
beta = +1
gamma = 0
