Radioactivity Flashcards
Why are some nuclei unstable
The number of neutrons inside it - too few or too many can affect the stability of
How do you predict which nucleus will decay next
You can’t, it is random
How is ionising radiation formed
When unstable nuclei decay
What does ionising radiation cause
Atoms to gain or lose electric charge, forming ions
What can we predict about the decay of a radioactive material
The PROBABILITY that a certain proportion of a radioactive material will decay in a given time
What are the three types of ionising radiation
- Alpha (α)
- Beta (β)
- Gamma (γ)
What are alpha particles
Fast moving helium nuclei (helium atoms with no electrons) that are thrown out of the unstable nuclei when they decay
What is the range and ionising power of alpha, beta and gamma
Alpha - short range, high ionising power
Beta - mid range, mid ionising power
Gamma - long range, low ionising power
How far can alpha particles move in air and through paper and why
Air - a few cm
Paper - a few mm
The range is low because they interact with atoms along their path, therefore rapidly giving up their energy
What is a beta- particle
Fast moving electrons that are ejected by a decaying nucleus.
How is a beta- particle ejected from the nucleus considering there are no electrons in a nucleus
In an unstable nucleus, a neutron can split into a proton and electron. The proton stays in the nucleus but the electron is ejected
What is the purpose of radioactive decay
For a nucleus to get a balance of protons and neutrons to allow it to be stable
How much heavier are alpha particles than beta particles
8,000
What is the relative charge of a beta- particle
-1
What is the relative charge of a beta+ particle
+1
Why do beta particles have a longer range than alpha, and why does this have an affect
They interact less frequently with matter in their paths because they are smaller and carry less charge
How far can beta particles travel through air and aluminium
Air - long distances
Alumulumu - 1-2 mm
What are gamma rays
Electromagnetic waves with very short wavelengths
What is the mass and charge of gamma radiation
Mass = 0
Charge = 0
What can you use to detect ionising radiation (2)
- Photographic film
- A Geiger-Muller tube
What is a Geiger-Muller tube
A tube that contains a gas that becomes ionised when radiation hits it, causing an electrical current which allows a counter to click up one.
It is used to find out the number of radioactive particles present
How else can we represent alpha particles
He (helium) or 4
He
2
What is the charge of an alpha particle
+2
What is the charge of a beta particle
-1
What is the nuclear equation for alpha decay
-4 from the mass number
-2 from atomic number
This will then form a new element. We must then add the helium at the end as a product
What would be the alpha-decay equation for uranium-238
U -> Th + He
Th - thorium. We use this because the mass number loses 4 and the atomic number loses 2
What is the nuclear equation for beta decay
The atomic number (small) goes up by 1 but the mass number (big) does not go up. Then an electron is added to the end e.g.
C -> N + e
What letter is used to represent an electron
0
e
-1
The mass number is zero but it has a charge of -1 so the atomic number is -1
What is the nuclear equation for gamma radiation
Nothing is changed because gamma rays are purely energy
E.g. Th - > Th + γ(gamma)
What is the equation for neutron emission
One is taken off the mass number but zero is taken off the atomic number. Then a neutron (n) is added to the end
What is the activity of a radioactive sample measured in
becquerels (Bq)
What happens to the activity of a radioactive sample as time goes on
It decreases
Are beta particles electrons from inside or outside the nucleus
Outside
What are 3 background sources of radioactivity in space
Comic rays
Solar radiation
Cosmic microwave background (CMB)
What are 3 background radiation sources from the earth
- Radon gas
- Gamma radiation from naturally occurring isotopes like uranium and thorium
- Rocks and soil (radioactive elements in the earth’s crust)
Design an experiment for determining the penetrating power of different radiation types
Put a Geiger-muller tube behind some materials/ further away from the radiation source, then test if it detects it or not. Then move on to the next radiation source. REPEAT. REMEMBER TO CHECK FOR BACKGROUND RADIATION AND SUBTRACT THIS FROM ALL READINGS.
Design an experiment for investigating the ionising power of different types of radiation
It is the opposite to the distance one - because if it has a high ionising power it will ionise the particles around it so will not travel a far distance. REMEMBER TO CHECK FOR BACKGROUND RADIATION FIRST AND SUBTRACT THIS FROM READINGS
