unstable nuclei that become stable by emitting radiation
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what are the three main types of radiation?
alpha, gamma , beta
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why is it impossible to predict when an unstable nucleus will decay?
it is a random process and is not affected by external conditions
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what was the plum pudding model?
the electrons were negative with surrounded with positive charge.
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what did Rutherford do ?
they fired alpha particles at gold foil and discovered the nuclear structure of an atom. He discovered alpha and beta rays, and proposed the laws of radioactive decay
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where is most of the mass of an atom concentrated?
the nucleus
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what are isotopes of an element ?
are atoms with the same number of protons but different number of neutrons
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how many protons do alpha particles have ?
two protons and two neutrons
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what happens when an unstable nucleus emits alpha particle ?
the atomic number (protons) goes down by two
mass number goes down by 4
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what's the relative mass of a beta particle ?
0 but its relative charge is -1
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what happens to the atomic number in a beta particle?
proton stays in nucleus so atomic number goes up by 1 the mass is unchanged. the electron is instantly emitted
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what happens when a nucleus emits gamma ?
the is no change to the atomic mass or the mass number. gamma is an electromagnetic wave released from the nucleus
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what stops alpha particles ?
paper
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what stops beta?
sheet of metal
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what stops gamma ?
lead
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what is the most ionising type of radiation?
alpha
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what's the least ionising type of radiation?
gamma
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what is the half life ?
the time taken for the radioactivity of a specified isotope to fall to half its original value
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what happens to the count rate and the atoms of radioactive isotopes?
they decrease by half every half -life
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what are radioactive isotopes used for in medicine?
they're used for medical imaging and treatment of cancer and as tracers for monitor organs
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what does a radioactive isotope depend on to be useful?
its half life
type of radiation it gives out
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why do they use gamma for cancer tumours?
because their beams can destroy cancer cells
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why do medical tracers have half lives of just a few hours?
this is so that the patient doesn't get exposure to unnecessary radiation
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what is nuclear fission?
is the splitting of an atom's nucleus into two smaller nuclei and 2 - 3 neutrons are released as is energy
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when does induced fission occur ?
when a neutron is absorbed y a uranium -235 nucleus or a plutonium -239 nucleus and then the nucleus splits
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why does a chain reaction occur in a nuclear reactor?
its when each nuclear fission event causes further fission events
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what do control rods do in a nuclear reactor?
they absorb fission neutrons t ensure that only one neutron per fission goes on to produce further fissions
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what is nuclear fusion?
the process of forving two nuclei close enough so that they form a single larger nucleus
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give an example of nuclear fusion?
the sun
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by what process is energy released from the sun ?
nuclear fusion
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what is a big technical problem with nuclear fusion
it is very difficult to get the right temperature for the nuclei to give them enough kinetic energy
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Other cards in this set
Card 2
Front
what do radioactive substances contain?
Back
unstable nuclei that become stable by emitting radiation
Card 3
Front
what are the three main types of radiation?
Back
Card 4
Front
why is it impossible to predict when an unstable nucleus will decay?
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