this presentation is about nuclear reactions

1. Nuclear Reactions
Rutherford’s Alpha Scattering Experiment

2. Describe how Rutherford showed that:
(a) The nucleus had a relatively small diameter
compared with that of the atom.
(b) Most of the mass of the atom is concentrated in
the nucleus.

3. In the early days of atomic theory, many physicists
tried to explain the model of an atom.
In 1902, Ernest Rutherford showed that alpha
particles emitted from the decay of unstable
radioactive materials were electrically charged
helium nuclei travelling at high speed.
In 1909, Rutherford used alpha particles to
investigate the composition of gold foil (i.e. to
explain the model of an atom).
IN THE BEGINNING……

4. To investigate the composition of gold foil using
alpha particles (i.e. to explain the model of an
atom).
Aim

5. Apparatus
Rutherford’s alpha scattering apparatus:
q
a-source
vacuum
gold foil
zinc sulphide
detector

6. Procedure
Rutherford fired alpha particles through a piece of
gold foil and used a zinc sulphide detector to detect
the scattered alpha particles and their location.

7. Results…..

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30. Rutherford’s experiment found that:
• Most of the alpha particles passed through the gold foil
undeviated.
• A few alpha particles were deflected from their path
but continued through the gold foil.
• A small number of alpha particles rebounded.
Results

31. • As most alpha particles passed through the gold foil
atoms undeviated, Rutherford concluded that most of
the atom was actually empty space.
From the results of his experiment, Rutherford explained:
• The deviation of some alpha particles from their
original path were due to positive charges within the
foil.
Conclusion

32. From the results of his experiment, Rutherford explained:
Conclusion
• A small number of alpha particles had rebounded
because they collided with something much larger and
heavier and which contains a concentrated region of
positive charge.

33. As a result of his observations, Rutherford suggested that
the atom had a positively charged centre which contained
most of the mass.
He called the
heavy positively
charged centre
the nucleus.
He went on to suggest that the nucleus was surrounded by
orbiting electrons required for electrical neutrality.
Conclusion

34. As a result of his observations, Rutherford suggested that
the atom had a positively charged centre which contained
most of the mass.
He called the
heavy positively
charged centre
the nucleus.
He went on to suggest that the nucleus was surrounded by
orbiting electrons required for electrical neutrality.
Conclusion

35. As a result of his observations, Rutherford suggested that
the atom had a positively charged centre which contained
most of the mass.
He called the
heavy positively
charged centre
the nucleus.
He went on to suggest that the nucleus was surrounded by
orbiting electrons required for electrical neutrality.
Conclusion

36. As a result of his observations, Rutherford suggested that
the atom had a positively charged centre which contained
most of the mass.
He called the
heavy positively
charged centre
the nucleus.
He went on to suggest that the nucleus was surrounded by
orbiting electrons required for electrical neutrality.
Conclusion

37. As a result of his observations, Rutherford suggested that
the atom had a positively charged centre which contained
most of the mass.
He called the
heavy positively
charged centre
the nucleus.
He went on to suggest that the nucleus was surrounded by
orbiting electrons required for electrical neutrality.
Conclusion

38. Modern measurements show that the average nucleus
has a radius in the order of 10-15 m. This is 100, 000
times smaller than the radius of a typical atom.