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Rutherford and Marsden's Scattering Experiment (continued).
From the results of the scattering experiment on gold
foil,
Rutherford and Marsden drew the following conclusions.
1. Since most of the a-particles went
straight through the foil,
most of the space taken up by the atoms must be empty.
2. Since some of the positively charged a-particles
were scattered back towards the
emitter,
they must have been repelled by a positive part (nucleus) of the atom.
3. Since the a-particles were
very fast moving,
the positive nucleus of the atom
must have a lot of mass
to be able to stop the a-particles moving forward and repel
them back again.
Their model of the atom
has a positively charged nucleus which contains the mass
and electrons in shells which have almost no mass
but
take up most of the space.
This is the model of atomic structure which we
use today.
In the above picture, the black circles represent the electron shells.
The a-particles travel straight through the
electron shells
without changing direction.
The red
circles represent the positive
nucleus.
If the a-particle gets close
to the positive nucleus
it is repelled and changes its direction.
The closer the a-particle gets
to the positive nucleus
the more it changes its direction.
If the a-particle goes straight towards the positive nucleus
it is repelled back towards the emitter.
This accounts for the scattering of
the a-particles from the gold
foil.
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