Experiment of Rutherford

The experiment of Rutherford was carried out in 1911 by Hans Geiger and Ernest Marsden under the direction of Ernest Rutherford, and showed that the part positively charged with the matter (which one calls now the Atomic nucleus) was concentrated in small points.

Previously, one knew just whom the matter comprised a negatively charged part (that one now calls electron S) that one could tear off (Cathode rays), and a positively charged part. One represented the matter like a “far with the prunes” (plum pudding) , a positive “paste” with negative inclusions. The experiment of Rutherford showed that it was the opposite.

Observation

The experiment is carried out under-vacuum. One places in a box of the radioactive matter emitting particles α which we direct in direction of a fine layer of Or (6000 Å). Behind this layer of gold, a screen is placed, it is enriched by a chemical substance (Sulfure of Zinc: ZnS) such as when the particles α will be posed above, they will be luminous.

Several minutes after the provision of the material, we see appearing on the screen various luminous points which are not at all in the orientation of the beam.

Interpretation

The majority of the particles α cross the gold sheet, without being deviated but part of these particles, about 0,01%, was deviated. From this experiment, we can deduce that the matter is a lacunar structure. It is primarily made up of Vide therefore the majority of the particles are not deviated. There exist the same small islands of positive load which push back the particles α. The order of magnitude of these small islands is infinitely small compared to the atom.

In fact, Rutherford observed the inelastic Scattering by thinking that it was the elastic Diffusion. The elastic rate of scattering is removed by a factor of form which takes into account the movement of the core like a positive cloud (or “paste”). Moreover, transmission of energy to the " noyaux" bound excites the atoms (inelastic scattering). Only the sum of all the various events (with participation of the neighbors thus) creates the image of a specific core (cf Discussion).

Implications

Following this experiment, Ernest Rutherford proposed a planetary model “” of the atom: the electrons, carrying the negative charges, were put into orbit around a very small positive core. This model was beaten in breach by two considerations:

• laws of the electromagnetism, and in particular the Maxwell's equations, which showed that a turning electron was to radiate energy and to thus slow down at the point to be crushed on the core;
• the fact that the interactions between the electromagnetic radiations were quantified (see black Corps and photoelectric Effet ).

See too

Internal bonds

• Diffusion Rutherford
• List of the scientific experiments