Gold Foil Experiment
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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.
Gold Foil Experiment
- 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 .