Ch25 - Radioactivity Flashcards
(29 cards)
What are the 3 types of radiation?
Alpha, Beta and Gamma
Why are gamma beta and alpha radiation known as ionising radiation?
Can ionise atoms by removing some of their electrons leaving positive ions
How can a cloud chamber be used to detect the presence of ionising radiation?
The cloud chamber contains ______ saturated with _____ at very low ______
The cloud chamber contains air saturated with vapour at a very low temperature
When air molecules are ionised liquid condenses onto the ions to leave tracks of droplets, making the path of the radiation.
What is the structure of alpha particles
Consists of positively charged particles
2 protons, 2 neutrons
Charge +2e
What is the structure of beta radiation?
Fast moving electron of positron
What is the structure of gamma radiation?
Consists of high energy photons with wavelengths less than about 10^-13m
No charge
Travels at the speed of light
Where are all forms of nuclei emitted from?
All form of radiation are emitted from the nuclei of atoms as a result of changes within unstable nuclei.
What experiment can be done to investigate the absorption of alpha beta and gamma.
A Geiger-muller tube and a counter may be used to investigate the absorption
|———->
| |———————|————->
|_| ———————» | ———————-»_space;|________________|————->
| |————>
Sealed Absorber GM tube To counter where count rate is taken
Source
What is one important precaution to take when taking the count rate of a radioactive material
Ensure that background radiation is measured beforehand and taken account for
Explain the absorption and radiation of alpha
(Why do they interact with surrounding particles)
Large mass and charge - means they interact with surrounding particles to produce strong ionisation
Therefore they have a very short range in the air
It only takes a few cm of air to absorb
Explain the absorption and radiation of beta particles
Beta particles have a smaller mass and charge that makes them less ionising
Longer range in the air approx 1m
1-3mm of aluminium required to stop
Explain the absorption and radiation of Gamma
Have no charge making them very little ionising
Count rate decays exponentially
Few cm of lead required to stop
What are the dangers of radioactivity
All types of radiation cause ionisation meaning they can damage living cells
Must be stored in a lead-lined storage container
Use tongs with long handles
What is transmutation
The process when one chemical element changes into another
This happens when the number of protons in an atoms nucleus changes because the number of protons determines what the element is
2 types : natural and artificial
What is natural transmutation
Happens on its own , throughout radioactive decay
What is artificial transmutation
Humans cause it by bombarding atoms with particles
Example:
In particle accelerators, scientists fire protons at nitrogen atoms to create oxygen
4
He
2
What is the nucleon number A and proton number Z
Nucleon number : 4
Proton number : 2
Neutron number 4-2=2
Alpha decay:
A C 4
X —> Y + He
Z D 2
A A-4 4
X —> Y + He
Z Z-2 2
What causes beta decay
Beta decay is caused by the weak nuclear force
Why does beta minus radiation occur
Beta Minus radiation is a result of too many neutrons for stability
What happens during beta minus radiation
A neutron decays into a proton, emitting an electron in the process, together with an anti-neutrino
Why does beta plus radiation happen?
Beta-plus radiation is caused by too many protons
How does beta plus radiation happen?
Weak nuclear force transforms protons into neutrons
In the process a positron is emitted with an electron neutrino
What causes gamma decay
Gamma decay is caused if a nucleus has surplus energy following an alpha or beta emission.
Gamma photons are emitted
