Geiger and Marsden Experiment setup

Geiger and Marsden Experiment setup

In order to understand the atomic structure, Rutherford came up with an experiment that was performed by Geiger and Marsden. Here is an experimental setup of the experiment

Geiger and Marsden Experiment setup

Observation obtained from the experiments

1) Large number of alpha particles passed straight through the foil without any deviation.

2) Very few particles approximately 0.14% deviated through an angle greater than 0.1⁰

3) 1 particle out of 8000 was deflected at an angle greater than 90⁰

4) Very few reflected back at 180⁰

This experiment was unable to explain JJ Thomson's atomic model. Thus rutherford came up with his conclusion. He explained that if most of the particles passed without any deviation, this signifies that the atom is almost an empty space. Rutherford argued with the observation that why few particles returned back straight? This concludes that alpha particles must have encountered a massive mass of positively charged particles. Thus from the experimental observation, he obtained the following conclusion:

Rutherford Conclusion 

1) Atom is 99.9% empty space.

2) Very little space 0.1% is occupied by a positive charge which he called a nucleus.

3) Almost all the mass of an atom is concentrated at the center.

4) Electrons revolve around the atom in a circular orbit similar to the solar system.

5) These electrons are held in the orbit due to the electrostatic force of attraction between electron and nucleus

Rutherford Atomic Model

Rutherford atomic Model

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Related Topics:  Atomic Structure      Geiger and Marsden Experiment     Atomic Spectra     Bohr's Postulate      Radius of an orbit      Velocity of an electron  Energy of an orbit      Limitation of Bohr's Model      De Broglie's explanation       Atomic Nucleus       Nuclear Binding energy        Radioactivity       Laws of radioactivity       Nuclear energy