Atomic Structure

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Plum pudding model
Sphere of positive charge with negative electrons embedded in it
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Who developed the Plum pudding model
J.J Thompson
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Who developed the nuclear model
Ernest Rutherford
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How did Rutherford disprove the plum pudding model
Gold foil experiment
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What particles were fired at the gold foil
alpha particles
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who discovered the neutron
James Chadwick
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mass number
the number of protons and neutrons in the nucleus of an atom
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atomic number
the number of protons found in the nucleus of an atom
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isotope
an atom with the same number of protons and electrons but different number of neutrons
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positively charged ions..
have lost electrons
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negatively charged ions..
have gained electrons
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what is an atom with too many or too few neutrons referred as
unstable
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what happens when an atom is unstable
it decays by emitting radiation
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what effect does alpha decay have on the nucleus of an atom
the mass number decreases by 4 and the atomic number decreases by 2
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what happens to the nucleus during beta radiation
a neutron turns into a proton and emits a fast-moving electron
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Gamma ray
Gamma ray emission causes no change in the number of particles in the nucleus meaning both the atomic number and mass number remain the same.
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which type of radiation is the most ionising
alpha particles
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which type of radiation is the least ionising
gamma
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which type of radiation is the most penetrating
gamma
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which type of radiation is the least penetrating
alpha
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How can radioactive decay be detected
geiger-muller tube
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Half-Life
Half-life is the time it takes for half of the unstable nuclei in a sample to decay or for the activity of the sample to halve or for the count rate to halve.
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Count rate
Count-rate is the number of decays recorded each second by a detector, such as the Geiger-Muller tube.
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irradiation
process of exposing an object to a source of radiation
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what is irradiation used for
to preserve fruit sold in supermarkets
sterilisation of surgical instruments
kill cancerous tumours
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advantages of sterilisation
can be done without high temperatures
can be used to kill bacteria on things that would melt
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disadvantages of sterilisation
may not kill ALL bacteria
can be very harmful – standing in the environment can lead to cell damage and mutation
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contamination
if radioactive material is mixed or dispersed within an object
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tracer
radioisotope used to trace eg the flow of blood through an organ
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contamination to check for leaks
build up of gamma emissions in a water supply can be found using a geiger muller tube
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differences between irradiation and contamination
irradiation occurs outside an object
it doesn't cause the object to become radio active
can be blocked with suitable sheilding
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what does radiation do to the human eye
High doses can cause cataracts.
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what does radiation do to the human stomach
Radioactive isotopes can sit in the stomach and irradiate for a long time.
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what does radiation do to the human reproductive organs
High doses can cause sterility or mutations.
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what does radiation do to the human skin
Radiation can burn skin or cause cancer.
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what can one do to reduce the risks of using radio active sources
- wear protective clothing to prevent the body becoming contaminated should radioactive isotopes leak out
- wear face masks to avoid breathing in materials
- handle radioactive materials with tongs in order to keep a safer distance from sources
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background radiation
low lever nuclear radiation that is always present from natural man-made sources
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name sources of background radiation
food and drink
cosmic rays
radon gas from the ground
buildings and the ground
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unit for radio activity
becquerel
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unit of radiation dose
sievert (Sv)
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Nuclear Fission
splitting of a large atomic nucleus into two daughter nuclei
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chain reaction
In addition to the 'daughter' products, two or three neutrons also explode out of the fission reaction and these can collide with other uranium nuclei to cause further fission reactions.
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Why do fission reactors have a graphite core
graphite slows the neutrons down so that they are more likely to be absorbed into a nearby fuel rod
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why do fission reactors have control rods
raised and lowered to stop neutrons from travelling between fuel rods and therefore change the speed of the chain reaction
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why do fission reactors have coolants
this is heated up by the energy released from the fission reactions and is used to boil water to drive turbines in the power station
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why do fission reactors have a concrete sheild
the daughter products of the fission reaction are radioactive and can be a hazard – an uncontrolled fission reaction is the basis of an atomic bomb
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Nuclear Fusion
two small, light nuclei join together to make one heavy nucleus
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why don't the two nuclei in fusion repel since they both have an overall positive charge
The fusion of the nuclei has to happen quickly so that the repulsion of the charges does not have time to stop it from happening.
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Other cards in this set

Card 2

Front

Who developed the Plum pudding model

Back

J.J Thompson

Card 3

Front

Who developed the nuclear model

Back

Preview of the front of card 3

Card 4

Front

How did Rutherford disprove the plum pudding model

Back

Preview of the front of card 4

Card 5

Front

What particles were fired at the gold foil

Back

Preview of the front of card 5
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