1. UNDERSTANDING
THE NUCLEUS
Rutherford
scattering
Chain
reaction
models

2. Chain reaction
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3. NUCLEAR FISSION IS WHEN A URANIUM NUCLEUS IS SPLIT BY A BOMBARDING
CHAIN REACTION
NUCLEAR FISSION IS WHEN A URANIUM
NUCLEUS IS SPLIT BY A BOMBARDING
NEUTRON
The nucleus splits into 2 smaller nuclei
Energy is released each time
a nucleus is split
More neutrons are released and
further fission can happen
This is called a chain reaction
HEAT
The new nuclei are radioactive
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4. 1 3 9 27 81
243
729
2187
6561
This simulation shows
how quickly the number
of nuclei undergoing
fission can grow if
a chain reaction occurs.
HEAT
Huge amounts of
heat will also be
produced when this happens
HEAT
HEAT
HEAT
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5. U + n Kr + Ba + 3( n) Kr Kr n n And so on…… n U n U n Ba Ba 235 1 90
143 1
U n Kr Ba ( n) 92 36 56 Kr Kr F i s o n F i s o n n n
And so
on…… n U n U n Ba Ba
NUCLEAR FISSION HAPPENS WHEN A URANIUM NUCLEUS IS
SPLIT BY A BOMBARDING NEUTRON.
The nucleus splits into 2 smaller nuclei and energy is released
as heat. These smaller nuclei are radioactive. More neutrons
are released and further fission happens. This is called a
chain reaction.
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6. (Discovery of the nucleus)
RUTHERFORD
SCATTERING
(Discovery of the nucleus)
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7. Alpha particles from a radioactive source
were fired, through a vacuum, at a piece
of gold foil.
The foil was extremely thin (less than 100
atoms thick).
Gold was a good material to
use because of it’s malleability.
The way the alpha particles travelled was
monitored.
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8. Gold foil Radioactive source Eventually a backscattered
alpha particle was observed.
Most of the alpha particles
passed through.
Radioactive
source
Most of the alpha particles
passed through the gold foil.
A small number came back
( were BACKSCATTERED).
What does this infer about
the structure of atoms?
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9. One in every 8000 alpha particles were
repelled backwards (back scattered).
What does this tell us about
most of the atom?
the centre of an atom?
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10. Paths through the atom No deflection – Alpha particle is not near the
nucleus
Small deflection – Alpha particle passes near
the nucleus and is repelled
Backscattered – Alpha particle travels directly
towards the nucleus and is repelled back
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11. Rutherfords findings: Most of the atom is empty (because so
many pass through the foil)
There is a very small in each atom
which contains almost all the of the atom.
The nucleus is charged so it
the alpha particles. (They are backscattered)
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12. Rutherfords findings: Most of the atom is empty space (because so
many pass through the foil)
There is a very small nucleus in each atom
which contains almost all the mass of the atom.
The nucleus is positively charged so it repels
the alpha particles. (They are backscattered)
answers
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13. Nuclear and
plum pudding
models
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14. - - - - - - - - - - - - + THE NUCLEAR MODEL (RUTHERFORDS)
THE OLD MODEL (PLUM PUDDING) - - - - - - - - + - -
SMALL, DENSE POSITIVELY CHARGED NUCLEUS - -
REGION OF POSITIVE CHARGE
WHICH SURROUNDS LOTS OF
SMALL NEGATIVE CHARGES.
LOTS OF
EMPTY SPACE
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15. END
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