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38 Cards in this Set
- Front
- Back
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Who came up with the plum pudding model? |
JJ Thompson |
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What were the bits of 'fruit' in the plum pudding model meant to represent? |
Electrons |
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Who proved the plum pudding model wrong and with what experiment? |
Rutherford , alpha scattering experiment |
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What was the expected result of the alpha scattering experiment? |
For the alpha particles to go through the gold sheet |
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How did the alpha scattering experiment prove the plum pudding model wrong? |
As although most particles did pass through the gold foil some deflected straight back, something the model couldn't explain |
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Who discovered that electrons orbit the nucleus in energy levels (or shells) |
Niels Bohr |
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Who proved the existence of the neutron? |
Chadwick, James Chadwick |
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What is the radius of an atom? |
1 × 10^-10 m |
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If an electron absorbs EM radiation what can happen? |
They gain energy and move to a higher energy level (shell), further from the nucleus |
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What is an isotope? |
An element that has a different amount of neutrons |
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What elements nucleus are alpha particles? |
Helium (2 protons, 2 neutrons) |
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How far can an alpha particles travel? |
A few cm |
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Why is an alpha particle so ionising? |
Because of its size (big) |
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What is alpha radiation used for? |
Smoke detectors - it ionised air particles, causing a current to flow. If there is smoke in the air, it binds to the ions - meaning the current stops and the alarm sounds |
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What is a beta particle? |
A fast moving electron from the nucleus |
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Where is a beta particle released from? |
The nucleus |
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Whats normally used to absorb a beta particle? |
Sheet of aluminium |
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For every beta particle emitted, a neutron in the nucleus has turned into what? |
A proton |
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What are gamma rays? |
EM waves with short wavelengths |
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What can gamma rays be absorbed by? |
Thick sheets of lead or concrete |
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What can beta particles be used for? |
Test the thickness of sheets of metal, as the particles are not immediately absorbed like alpha rays and don't penetrate as far as gamma rays |
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Order the types of radiation from most to least ionising: |
1. Alpha 2. Beta 3. Gamma |
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Write a nuclear equation of alpha decay, starting with uranium. (238 mass, 92 atomic number) (becomes thorium) |
Uranium (238, 92) -----> Thorium(234,90) + alpha particle(4,2) |
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Why does beta decay change the element it leaves? |
Because one of the neutrons in the nucleus becomes a proton and therefore the atomic number changes, changing the element |
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Write the nuclear equation of beta decay of carbon 14(6) to nitrogen |
Carbon (14,6) -----> Nitrogen (14,7) + beta particle (0,-1) |
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How can you measure radiation given out? |
Use a Geiger meter which records a count rate |
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What does a Becquerel measure? |
How many decays per second (i.e 1 Bq = 1 decay per second |
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Define a half life : |
The half life is the time taken for the number of radioactive nuclei in an isotope to halve. Or Time taken for the activity to fall to half of its initial value |
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If the initial activity of a radioactive nuclei is 1600 and it takes 4 seconds to get to 800, how long would it take to get to 200 (from 1600)? |
12 seconds 1600-800 = 4 seconds 800-400 = 8 seconds 400-200 = 12 seconds |
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What can exposure to radiation cause? |
Damage to cells and therefore often cancer |
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What is irradiation? |
Exposure to a radioactive source |
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How can you avoid irradiation while working with a radioactive source?(2) |
Keep sources in lead-lined boxes Stand behind barriers Stand in a different room and use machines to handle it |
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Define contamination: |
When radioactive atoms get onto or into an object |
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If you touch a radioactive source is that irradiation or contamination? |
Contamination, as it is on you |
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How to avoid contamination:(2) |
Wear gloves and tongs to stop particles getting under your fingernails / skin Wear protective suits to stop you breathing in particles |
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Which types of radiation are most dangerous in irradiation form? |
Beta and gamma as they can penetrate your body and get to delicate organs, whereas alpha can't |
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Why is alpha so dangerous if you become contaminated with it? |
Because all their high ionising damage is in a small area and if it's inside you it will do tons of damage |
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:) |
