Physics Unit 2.5 What happens when radioactive substances decay, and the uses and dangers of their emissions.

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What is an isotope?
They contain equal numbers of protons but different numbers of neutrons in their nuclei.
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Substances that constantly emit radiation are said to be ...
Radioactive.
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Describe the plum pudding model.
A sphere of positive charge, with negative electrons scattered amongst it
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Describe the Rutherford scattering experiment.
An alpha particle was fired by a atom shooter, through golden foil, which was then detected by a Gieger counter.
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Describe the results of Rutherford's experiment.
1)- Lots were detected behind the gold, they must have traveled straight through. 2)- Some were deflected. Positive alpha particle repelled. 3)- Few detected in front of gold. Alpha particle must've bounced off something.
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What atom model replaced the plum pudding?
Nuclear atom.
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Describe the difference between the nuclear atom, and the plum pudding model.
The plum pudding was a positively charged sphere, with electrons dotted around. Nuclear atom had a central nucleus, (which had solid matter), with electrons orbiting the nucleus in shells.
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Describe alpha particles.
Two neutrons and two protons, the same as a helium nucleus. A sheet of paper stops alpha radiation, because the particle is so big. Slow moving. Highly ionizing.
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Describe beta particles.
An electron from the nucleus, which has high energy (fast). Few mm, so Al can stop it. Weakly ionizing.
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Describe gamma radiation.
It is electromagnetic radiation. Very small. Reduced by a few cm of lead. Very weakly ionizing. No mass/atomic no. 3x10^8m/s fast.
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Alpha and beta radiations are deflected by both electric and magnetic fields but gamma radiation is not.
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Alpha particles are deflected less than beta particles and in an opposite direction.
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Describe the dangers of alpha radiation, inside the body.
Is most dangerous out of beta, and gamma radiation. It is easily absorbed by cells.
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Describe the dangers of beta, and gamma radiation, inside the body.
Beta and gamma radiation are not as dangerous because they are less likely to be absorbed by a cell and will usually just pass right through it.
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Describe beta, and gamma radiation outside the body.
Beta and gamma radiation are the most dangerous sources because they can penetrate the skin and damage the cells inside.
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Describe alpha radiation outside the body.
Alpha radiation is not as dangerous because it is unlikely to reach living cells inside the body.
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Describe half-life.
The half-life of a radioactive isotope is the average time it takes for the number of nuclei of the isotope in a sample to halve, or the time it takes for the count rate from a sample containing the isotope to fall to half its initial level.
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What does Carbon14 deay into during radioactive decay?
Nitrogen14 - which explains why there is so much N in the atmosphere.
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What is the difference between gamma decay, and beta/alpha decay?
Gamma does not change the atom. Beta, and alpha decay change the element.
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Why is alpha radiation so ionizing?
It is a big particle, and slow, so there is more chance of colliding electrons from other atoms.
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Other cards in this set

Card 2

Front

Substances that constantly emit radiation are said to be ...

Back

Radioactive.

Card 3

Front

Describe the plum pudding model.

Back

Preview of the front of card 3

Card 4

Front

Describe the Rutherford scattering experiment.

Back

Preview of the front of card 4

Card 5

Front

Describe the results of Rutherford's experiment.

Back

Preview of the front of card 5
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Comments

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ellybeanzz

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ellybeanzz

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