Ernest Rutherford conducted the gold foil experiment to test J.J. Thomson's "plum pudding" model of the atom. In the experiment, Rutherford bombarded a thin gold foil with alpha particles and observed their scattering. Most alpha particles passed straight through, but some were deflected, and a very small number bounced straight back. This showed that the atom is mostly empty space, with a small, dense, positively charged nucleus at its center containing almost all its mass - contradicting Thomson's diffuse model. The experiment provided evidence for Rutherford's nuclear model of the atom.

1. Gold Foil
Experiment
Ernest Rutherford

2. Ernest
Rutherford
 He is a British physicist and
chemist and known for his
remarkable orbital theory of
the atom in his discovery of
Rutherford dispersion with his
famous Gold Foil experiment.
 He is also known as the “father
of nuclear physics”.
 He was honored with a Nobel
Prize in Chemistry in 1908 for
his exploration into the
disintegration of the elements,
and the chemistry of
radioactive substances.

3. Gold foil Experiment
 helped describe the nuclear structure of the atom.
The deflection of alpha particles implied the
existence of a dense, positively charged central
region containing most of the atomic mass.
 Rutherford's Gold Foil Experiment proved the
existence of a small massive center to atoms, which
would later be known as the nucleus of an atom.

4. What is the purpose?
 The purpose of the experiment
is to test the Plum-Pudding
model of J.J. Thomson

5. Hypothesis of the Experiment
If Thomson’s model is correct, high velocity of
alpha particles should pass through the foil in
straight line because:
1. The mass of the atom is spread out trough
the atom .
2. Very little deflection of the beam of
positively charged particle will result from
the repulsion of the positively-charge
material; and
3. Slight deflection due to collision with
other atom.

6. Illustration of Gold Foil
• Most of the alpha particles went straight through and
a very small number / a few bounced back / were
reflected.
• Some of the alpha particles were deflected

7. What did Rutherford do in the
experiment?
 Rutherford and his companions (Hans Geiger,
a German physicist and Ernest Marsden, an
English physicist) hammered a gold foil to a
thin sheet approximately 8.6 x 10^(-6)
centimeters thick.
 The experiment was performed in complete
darkness in order for the light of the alpha
particles to be observed.

8. Observations:
About 99.9% of the alpha particles passed through
the foil in straight lines
Some were slightly deflected from expected path
Few of the alpha particles were deflected at a right
angles and few were reversed in direction.

9. Conclusions:
 Most of the atom was empty space because most
of the alpha particles went straight through.
 The nucleus was positively charged because the positive
nucleus repelled the positively charged alpha particles.
 The mass of the atom was concentrated in the
nucleus / the nucleus is very dense (not “large or
heavy”) because the alpha particles were repelled
straight back / at large angles
.