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Rutherford and Marsden's Scattering Experiment.
Continued from the previous page.

What were the Conclusions
from Rutherford and Marsden's Scattering Experiment?

From the results of the scattering experiment on gold foil (see below)
Rutherford and Marsden drew the following conclusions.

1. Since most of the alpha particles went straight through the foil
of the space taken up by the atoms must be empty.

2. Since some of the positively charged alpha particles
were scattered back towards the emitter, they must
have been repelled by a positive part of the atom (the nucleus).

3. Since the alpha particles were very fast moving,
they have a relatively large momentum.
The positive nucleus of the gold atom must have a large mass
to be able to stop some of the alpha particles
from moving forward and then repel them back again.

The Conclusion of Rutherford and Marsden's Scattering Experiment

In the above picture, the black circles represent the
electron shells. The alpha particles travel straight
through the electron shells without changing direction.

The red circles represent the positive nucleus.
If the alpha particle gets close to the positive nucleus
it is repelled and changes its direction.
The closer the alpha particle gets to the positive nucleus
the more it changes its direction.

If the alpha particle goes straight towards the positive nucleus
it is repelled back towards the emitter. This accounts
for the scattering of the alpha particles from the gold foil.

Rutherford and Marsden's model of the structure of the atom
has a small positively charged nucleus which contains
nearly all of 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.

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