Radioactivity Flashcards
Define a radioactive substance
A radioactive substance releases nuclear radiation which is a type of ionising radiation emitted from matters with an unstable nucleus
Why are nuclei unstable
If they have an unequal number of protons and neutrons
What are isotypes
Atoms of the same element with different numbers of neutrons
What are the three types of radiation?
Alpha, beta, and gamma
What is the nature of radioactive decay
It is completely random
Can we predict the decay of a specific individual atom?
No, but we can estimate the half life of a large group of them
Define half life
The time it takes for the number of nuclei to halve, or for the count rate of radioactive radiation to halve
Note some uses for radioactive materials
- Measuring thickness
- Sterilisation
- Smoke alarms
- Cancer treatment
- Carbon dating
What is the meaning of the atomic number and mass number?
Atomic numbers are unique to each element, and is equal to the number of protons present in the nucleus. The mass number is the sum of protons and neutrons. The mass number goes higher.
What do isotopes have
Different mass numbers
What is an alpha particle equal to
A helium nucleus: two protons and two neutrons
How can equations for alpha decay be written
Basically using the adjusted Helium symbol (He2+), and making sure that all of the bits on the top and bottom add up at the end.
Describe alpha radiation
Slowly moving and strongly ionising. It has little penetrating power, and it’s range is apparently -5cm. It can be stopped by thin paper.
What is beta radiation
The equivalent of a high energy electron
What is the charge and mass of beta radiation
-1 charge and a negligible mass
What represents Beta?
A ß thingy always with a 0 on top and -1 at its base
How quickly does beta move and how ionising is it
It is faster moving but less strongly ionising. Its range is up to one metre, and it can be absorbed by thin metal
What is gamma radiation
Not a particle but a type of electromagnetic radiation. It is a wave, meaning that it has no mass or charge
How quickly does gamma travel and how ionising is it
At the speed of light, but it is only weakly ionising
What is required to absorb gamma
A thick lead block
List some natural sources of radiation
Cosmic rays, rocks and even living things
List some man made sources of radiation
X-Rays, nuclear power stations, nuclear weapons
What is the difference between fission and fusion?
Fission breaks atoms apart and fusion brings them together
What happens in fission
One single neutron starts the reaction, in turn releasing 2 or 3. In the correct environment, these can go on to release yet more.
How do we prevent chain reactions from getting out of control
Control rods are key, absorbing 2 out of every 3 electrons released in every reaction. The moderator also slows the neutrons released to ensure they can be absorbed by uranium nuclei, to cause another reaction
What does the concrete shield do
It ensures that no radiation escapes
What fuels nuclear reactions
Uranium
What slows neutrons
The graphite moderator
What will be the fuel for fusion
Deuterium
What conditions would be needed for successful fusion
High temperature and pressure
