P2 Radioactivity

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  • Created by: KAustria
  • Created on: 17-05-14 15:25
What are the nuclei of radioactive substances like?
They are unstable
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How do radioactive substances become stable?
They become stable through radioactive decay which involves them emitting radiation and turn into other elements.
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What are the 3 types of radiation?
Alpha radiation, Beta Radiation and Gamma Radiation
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Why can't we predict when an unstable nucleus will decay?
It is a random process which is not affected by external conditions.
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Give examples of background radiation
Radiation from space, Food and Drink, X-ray tubes and rocks
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What happens to the rate of radioactive decay if the temperature is doubled?
Nothing because radioactive decay is not influenced by external conditions.
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What was the plum pudding like?
Scientists believed atoms were consisted of spheres of positive charge with electrons stuck on them.
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What were results of the alpha partical scattering?
Alpha particles were fired at thing gold foil 1. Most atoms passed through = Most of atom is empty space 2. Some atoms deflected through small angles = Nucleus is positve 3. A few rebounded a large angles = Nucleu has a large mass and positive charge
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Why did most alpha particles pass straight through the foil in Rutherford's experiment?
Most of the atom is just empty is space
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Why did the alpha particles rebound?
Alpha particles have a positive charge so they must have been repelled by another positive charge.
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Describe the structure of an alpha particle?
1. 2 protons , 2 neutrons 2. Mass of 4 3. Charge of +2
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What happens to the nucleus of an element when it emits alpha particles?
1. Atomic number goes down by 2 2. Mass number goes down by 4
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Describe the structure of Beta Particle
1. High speed electron from the nucleus 2. Emitted when a neutron in the nucleus changes into a proton and an electron 2. Relative mass is 0 and its charge is -1
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What happens tot he nucleus of an element when it emits Beta particles?
1. The proton stays in the nucleus 2. Atomic number goes up by one 3. Mass number is unchanged. 3 Electron is instantly emitted.
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What happens to the nucleus after emitting gamma radiation?
No change in the atomic number and the mass number because gamma rays are electromagnetic waves that have no charge or mass.
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What is ionisation?
When nuclear radiation travels through material colliding with the atoms and turning them into ions because electrons have been knocked off.
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What can occur when ionisation takes place?
Ionisation in a living cell can damage or kill the cell.
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What are the 4 main key points of alpha particles?
1. They are large so they can cause lots of collisions and therefore they are strongly ionising 2. Alpha particles do not penetrate far 3. Stopped by a thin sheet of paper, human skin or air 4. Positive charge so are deflected by elec/mag fields.
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What are the 3 main key points of beta particles?
1, Smaller and faster than alpha so they are less ionising 2. Penetrate further- stopped by thin sheet of aluminium 3. Deflected in the opposite direction to alpha in magnetic field because it is -1
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What are the 4 main key points on gamma radiation?
1. Electromagnetic waves so they travel a long way through material 2. Weakly ionising and very penetrating 3. Several cm of lead and several m of concrete absorb it 3. They are not deflected by electric and magnetic fields.
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Which type of nuclear radiation is the least penetrating?
Alpha
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Which type of nuclear radiation is the least ionsing?
Gamma
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What is half life?
The average time it takes for the number of nuclei of the isotope in a sample to halve (decrease in radioactivity).
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How can you measure the radioactivity of a saple?
Measuring the count rate
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How is activity of a radioactive source measured?
The umber of nuceli that decay per second.
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What are alpha particles used in at work?
They are used in smoke alarms and need a half life of several years.
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What are Beta sources used for?
1. Monitoring the thickness of foil and paper. It needs a half life of several years so the decrease in count rate are due to changes in the thickness of the paper.
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What are Gamma and beta sources used for?
1. Tracers in medicine where the sample is detected by a detector outside the patient. Needs a half life of several hours so that the patient is not exposed to unnecessary radioactivity.
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What is radioactive dating?
Used to find the age of ancient material. Carbon dating is used in organic material. Uranium dating is used in igneous rock
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Other cards in this set

Card 2

Front

How do radioactive substances become stable?

Back

They become stable through radioactive decay which involves them emitting radiation and turn into other elements.

Card 3

Front

What are the 3 types of radiation?

Back

Preview of the front of card 3

Card 4

Front

Why can't we predict when an unstable nucleus will decay?

Back

Preview of the front of card 4

Card 5

Front

Give examples of background radiation

Back

Preview of the front of card 5
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