Suggested the plum pudding model. Tiny negtive electrons stuck in spheres of positive charge.
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1909 Rutherford carried out the
Alpha scattering experiment. Which disproved the plum pudding model as some particles were deflected back the way they had come which the plum pudding couldn't explain.
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Half life is
The time taken for the number of radioactive nuclei in an isotope to halve.
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Radioactive substances give out
Radiation from the nuclei of their atoms no matter what. Radiation is measured with a Geiger-Muller tube and counter.
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Radioactive decay is
Random.
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Background radiation comes from many sources eg
Naturally occuring unstable isotopes in the air,food, building materials and rocks, from space and from human activity eg nuclear explosions.
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Exposure to radiation is called
Irradiation
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Contamination is when
Radioactive particles get into or onto an object. They might decay and could cause harm.
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Isotopes are
Different forms of the same element. So have same number of protons but different number of neutrons.
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Alpha particles are
Helium nuclei, 2 neutrons and 2 protons which don't penertrate far and stop quickly, few centimeters in air and are absorbed by a sheet of paper. Highly ionising
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Beta particles are
High speed electrons released by the nucleus. Moderately ionising, penetrate moderately far, range of a few metres in air
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Gamma rays are
Elcectromagnetic waves with a short wavelength released by the nucleus. Penetrate far into materials, have a long distance in air. Weakly ionising - tend to pass through rather than colliding with atoms. Absorbed by sheets of lead or metres of concre
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When an atom emits an alpha particle
It's atomic No. reduces by 2 and it's mass number reduces by 4
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When beta decay occurs
A neutron turns into a proton/increasing the + charge of nucleus/mass of nucleus doesn't change/
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Gamma rays don't
Change the mass or charge of the nucleus
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Risks of radiation include
radiation entering living cells - ionising atoms and causing tissue damage
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Lower doses of radiation
cause minor damage not killing cells but they can become mutant cells which divide uncontrollably = cancer
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Higher doses of radiation
Cause radiation sickness and tend to kill cells completely
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Gamma rays are used
to treat cancer
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Gamma rays are used as
medical tracers eg iodine 123 - thyroid
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Nuclear fission is
splitting a large unstable nucleus which releases energy
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Nuclear fusion
joining together small nuclei
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Other cards in this set
Card 2
Front
1909 Rutherford carried out the
Back
Alpha scattering experiment. Which disproved the plum pudding model as some particles were deflected back the way they had come which the plum pudding couldn't explain.
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