CP6 Flashcards
Diameter of an atom
10^-10m
Diameter of nucleus
10^-15m
Electron movement
- Electrons orbit the nucleus in different orbits of energy leaves
- An electron will move from a lower to a higher orbit if it absorbs electromagnetic radiation
- An electron will move from a higher to a lower orbit if it emits electromagnetic radiation
Ionizing radiation
Alpha, beta, gamma and neutron radiation are emitted by unstable nuclei
Alpha particles
Will travel 5cm in air
Very ionizing
Can be stopped by a piece of paper
Beta particles
Will travel a few meters in air
Moderately ionizing
Can be stopped by aluminum
Gamma rays
Will travel a few km in air
Weak ionizing
Need thick lead to stop them
Background radiation
low levels of radiation that are present all the time. Both natural and man made.
Measuring radioactivity
Geiger-muller tube detects nuclear radiation. It is connected to a counter which shows the amount of radiation that has been detected
Beta decay
When unstable nuclei undergo radioactive decay (there are two types- one where an electron is admitted and one where a positron is emitted)
Beta-minus decay
A neutron decays to become a proton and an electron. The proton stays with the nucleus but the electron is emitted at a high speed.
Beta-plus decay
A proton decays to become a neutron and a positron. The neutron stays in the nucleus and the positron is emitted at a very high speed carrying a positive charge
Uses of beta decay
Carbon-14 is used for radiocarbon dating which finds the ages of materials that are very old.
Half life
The time it takes for half of the unstable atoms to decay
Uses of gamma rays
- Killing cancer cells
- Sterilise hospital equipment
Use of alpha particles
- Smoke alarms
Danger of radiation
Ionizing radiation can knock electrons out of atoms, turning them into ions. This can be very damaging to humans
Radiation precautions
- Limiting the time of exposure to radiation
- Wearing protective clothing that absorbs radiation
- Increasing the distance between the person and the source of radiation
Irradiation
Irradiation is ionizing radiation from an external radioactive source traveling to the body (it is not breathed in, eaten or drunk)
External Contamination
Occurs when radioactive materials come in contact with a persons hair, skin or clothing
Internal Contamination
Occurs when a radioactive source is eaten or drunk
Medical uses of ionizing radiation
- Tracers
- PET scanners
- Treating tumors internally
- Treating tumors externally
Medical traces
- Substances that contain radioisotopes
- The radiation emitted by the tracer can be detected and the biological process monitored
- Doctors can diagnose the nature and the location of any health problems
Treating tumors internally
- Radioisotopes are injected/ are injected by eating or drinking
- The radiation emitted kills cancer cells
Treating tumors externally-
- Beams of gamma rays are fired from different angles towards the cancer
- Each beam is not damaging enough to kill it, but damages it
- The amount of ionizing radiation that the surrounding tissue receives is reduced
Nuclear power
Nuclear power is a highly efficient way of producing electrical energy. However nuclear power stations do produce a lot of radioactive waste that has to be dealt with.
Eval of nuclear power
:) Does not produce carbon dioxide
:) Supplies of carbon dioxide will last longer than fossil fuels
:( Difficult and expensive to store safely
:( An accident in a nuclear power station can spread radioactive material over a large area
Nuclear fusion
Nucleus fusion involves the joining of smaller nuclei to form larger nuclei. Nuclei need to get very close together for fusion to happen. Under normal conditions, nuclei repell eachother. Very high temperatures and pressures are required to overcome this electrostatic repulsion.
Nuclear fission
In a fission reaction, a large unstable nucleus splits into two smaller ones (e.g a uranium-235 nucleus splits up when it absorbs a neutron. It produces two daughter nuclei, two or more neutrons and releases energy)
Chain reactions
The neutrons released by the fission of U-235 may be absorbed by other nuclei. Each of these may undergo fission and produce even more. This is called a chain reaction If a chain reaction is not controlled there will be an explosion.
