Radioisotope: an unstable isotope that spontaneously changes its nuclear structure and releases energy in the form of radiation.
Isotopes
StableRadioisotopes
Unstable
An unstable atom with a nucleus that can spontaneously disintegrate is said to be radioactive.
Abundant
Stable Isotopes
β+decay
β- decay
Radioactive Isotopes
These are just a few examples, there are more stable and unstable isotopes for tin!
AbundantAll isotopes of Uranium are
radioactive. None are stable.
...
IsotopesStable
Radioisotopes
Unstable
How long does it take for a radioactive atom to disintegrate? How do we find out?
Half-life: the average length of time it takes radioactive material to decay to half of its original mass
The half life of Cobalt-60 is 5.27 years. Does that mean that it takes 5.27 years for an isotope atom to decay?
Examplehalf life of Cobalt-60 is 5.27 years
It takes 5.27 years for the sample to decay to half of it’s original mass
100 g 50 g81 g 69 g
50 g counting only the blue Cobalt-60 atoms
Example continuedWhat if we wait another 5.27 years?
50 g
It takes 5.27 years for the sample to decay to half of it’s original mass
25 g32 g
Trying it outCarbon-15 has a half-life of 2.5 s.
If the sample is 100g, how much carbon-15 will be remaining after 10s?
Time (s) Mass of carbon-15 (g)
0 100
2.5 50
5 25
7.5 12.5
10 6.25
ApplicationsWhich elements are used for determining the
age of:
- a living thing that has died
- the moon or the earth
Explanation together.
Nuclear Fission
Same amount of energy in one reaction as about 7 million times as great as the energy released when the same mass of dynamite explodes.
Heavy water: water that contains a high level of deuterium
Nuclear CANDU ReactorOur focus in this course: the transformations
of energy.
Photo source: http://www.nucleartourist.com/type/candu.htm
Nuclear fission produces neutrons and thermal energy.Heavy water moderates neutrons and absorbs thermal
energy.Thermal energy is transferred to the steam generator.Heavy water cools and flows back.Normal water absorbs thermal energy and vaporizes into
steam. Steam pressure builds and transforms thermal energy into
mechanical energy causing the turbine to turn.The electrical generator converts the mechanical energy into
electrical energy.
Nuclear FusionNuclear fusion: a nuclear reaction in which
the nuclei of two atoms fuse together to form a larger nucleus.
Proton-proton chain
CNO chain
Photo source: http://en.wikipedia.org
Nuclear FusionNuclear fusion produces significantly more
energy per mass of fuel than fission reactions.The only man-made fusion device to achieve
ignition to date is the hydrogen bomb.Nuclear fusion occurring in stars.
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