P7: Radioactivity Flashcards
What is radioactive decay
When an unstable nucleus will become more stable over time by spontaneously (random) emitting ionising radiation.
What are the names of substances that decay radioactively
Radioactive substances
What are the three types of ionising radiation
Alpha
Beta
Gamma
What is alpha radiation
A type of radiation produced by alpha decay.
It releases helium nuclei, known as alpha particles
What is beta radiation
Another type of radiation produced by beta decay. It releases electrons known as beta particles
What is gamma radiation
Final type of radiation produced by gamma decay. It is a high electromagnetic energy wave with higher frequencies than X Rays
What is an alpha particle
Helium nuclei
What is a beta particle
Electron
What is a fact about radioactive decay
Unpredictable
We cannot predict when atoms will emit ionising radiation
What are the three ways we can detect radioactivity
Cloud chambers
Photographic film
Geiger counter
What is a cloud chamber
Containers full of air containing alcohol vapour.
Ionising radiation enters the air and leaves a trail of ionised air molecules.
The alcohol vapour condenses on the ionised air molecules, showing the trail of radiation
What is the effect of the photographic film
Ionising radiation shares the same effect with this and light.
A bright spot appears wherever ionising radiation hits the film
What is a geiger counter
Ionising radiation enters a tube of low pressure gas. Atoms in the gas are ionised, knocking electrons out of the atom. Gases then conduct electricity and completes an electric circuit.
When radioactive substances enter a Geiger counter, it makes a clicking noise
What is background radiation
This is when atoms or isotopes are very common, they even exist in our body.
They decay radioactively, meaning we are always surrounded by background radiation
What is the count rate for geiger counters
Number of decays recorded per second
What are sources of background radiation
Foods
Radon gas
Rocks
Sun
What are the properties of an alpha particle
An alpha particle contains 2 protons and 2 neutrons.
This creates a relative mass of 4 for an alpha particle.
Alpha particles are big and heavy so alpha radiation is strongly ionising.
They do lots of damage, but can be stopped by small amounts of matter such as paper
What are the properties of a beta particle
A beta particle is made up of high energy electrons.
Beta radiation is more penetrating than gamma radiation but less ionising than alpha radiation.
It can pass through paper but is stopped by aluminium foil
What are the properties of gamma radiation
Gamma radiation is the least ionising of the three.
It does deal less damage than alpha and beta radiation and cannot be stopped by ANYTHING
How does penetration link to ionising radiation
Strongly ionising radiation is less likely to penetrate materials. It damages materials much more so it comes to a stop soon.
Out of the three types of radiation, which is the most penetrating and ionising
Gamma is the most penetrating
Alpha is the most ionising
How can we test beta radiation
Paper production
Beta particles are able to be chucked through paper to observe whether the paper produced is the right thickness.
What if the paper is too thick to detect beta radiation
Fewer beta particles reach the detector. Production is then stopped
How can we test alpha radiation
Smoke detectors
A radioactive material fires alpha particles at a smoke detector.
What happens if smoke comes in contact between the two objects
Less alpha particles will reach the detector, setting off the smoke alarm
What are ways to test gamma radiation
Sterilisation: we can use gamma radiation to sterilise medical equipment in hospitals, which can kill bacteria and viruses
Internal organ exploration: If a gamma emitting isotope is put into a patient’s body, we can follow the radiation’s movement around the body. Due to being the most penetrating type, it can pass through objects more easily than beta and alpha radiation. This means gamma can leave the body without creating too much damage (ionisation).
Gamma radiation also has a short half life meaning radiation vanishes quickly
What is nuclear fission
Nuclear fission splits 1 nucleus into 2 smaller nuclei, which normally takes place in nuclear reactors.
A neutron collides with a large nucleus and is absorbed. This forms an unstable nucleus.
The nucleus then splits into fragments. This releases large energy amounts and more neutrons. Neutrons can often collide with nuclei.
Energy released is then used to boil water, which rotates a turbine. The turbine then turns a generator, producing electricity
What happens if nuclear fission isn’t controlled?
The rate of nuclear fission becomes faster and faster. This creates a chain reaction where each fission stage produces more and more energy. This can lead to an explosion
What are atom bombs
Atom bombs use these chain reactions to create large explosions and emit lots of energy
What is nuclear fusion
Nuclear fusion joins 2 smaller nuclei to create 1 large nucleus. Creating this large nucleus releases energy
What are hydrogen bombs
Hydrogen bombs use nuclear fusion to release lots of energy in an explosion
What do stars use to generate energy
Nuclear fusion
What is the difference between nuclear fusion and nuclear fission
Nuclear fission: Imagine a raindrop splitting when coming across an object.
Nuclear fusion: Imagine two raindrops colliding to form a new larger raindrop
What happens in alpha decay
In alpha decay, 4 nucleons (protons and neutrons combined) are lost in the form of an alpha particle. 2 protons are lost so the initial atom becomes a different element
What happens in gamma decay
In gamma decay, 0 nucleons (protons and neutrons combined) are lost in a gamma ray. The element does not change when gamma rays are emitted
What happens in beta decay
In beta decay, 1 electron is carried away. The number of nucleons (protons and neutrons combined) stays the same but nitrogen is formed from the original carbon.
What is a nuclear fission equation
The number of protons remains the same but 4 nucleons (protons and neutrons combined) are released to continue a chain reaction with other atoms
What happens during alpha, beta and gamma decay
An unstable nucleus becomes more stable
Which isotope of uranium is used in nuclear fission
Uranium-235
What is the product of beta decay of a carbon atom
A nitrogen ion and an electron
What is half life
The average time taken for the number of radioactive nuclei to halve.
What is the activity of radioactive substance measured in
Becquerels (Bq)
What two adjectives describe half lives
Constant: half life for any isotope of an element is constant. The half life of unstable isotopes can be seconds or millions of years
Unpredictable: Half life for any isotope of an element is unpredictable, despite large amounts of nuclei behaving in predictable ways.
How can we find the half life of an isotope from graphs or tables
Measure the time it takes for the radioactive count rate or the number of unstable nuclei to halve
How do we work out substance radiation
Total radiation - Background radiation
How can we calculate the half life of a radioactive isotope
Strip out the background radiation of the environment around us.
What is the calculation to find out the level of radiation due to substance
Level of radiation with substance and background radiation - Level of background radiation
What can we use to find out the level of background radiation
Geiger counters
What damage can ionising radiation cause
Failed organs due to mutations that lead to cancer, and cell damage
Half life question
An element has a half life of 5 years.
If there are 571g of the element in a substance, how much is left after 15 years?
After 15 years, the amount of the element will have been halved 3 times
15/5 = 3
So the amount left in the sample is
571 x 1/2 cubed = 71.375 g
What are the safety precautions of ionising radiation damage
Reduced exposure
Storage
Usage
Handling
