Educational physics animation : To see the invisible needs extraordinary vision, the discovery of nucleus was a landmark event that changed the course of science and development in this world leading to creation of nuclear power plants and ironically nuclear bombs. Lets see how this discovery was made by these extraordinary men.

The science animation explains the following in a story like manner using in-depth explanation, the discovery of nucleus.

Lord Rutherford while studying the nature of the Curie's radiation discovered that the radioactive elements emit three types of radiations with different penetrating power namely alpha (least penetrated), beta (moderately penetrating) and Gamma (highly penetrating). When these radiations were subjected to electric fields, alpha rays were found to be positively charged particles while beta rays were found as negatively charged light particles. Gamma rays were found to be neutral in nature.

While studying the properties of these radiations, Rutherford noticed that the beam of alpha rays when were made to fall on a photographic plate by passing it through air, the edges of the slit became diffused and widened. He concluded that the alpha rays were scattered by air molecules.

To get a clearer evidence about the scattering he along with his co-workers Geiger and Marsden built an apparatus to bombard alpha particles on thin metallic foils. The metallic foil he selected for his experiment was a very thin gold foil.

Now if the atoms were actually arranged according to Thomson, then the alpha particles would go undeflected. But during experimentation it was found that though most of the alpha particles went right through the thin foil, a few alpha particles rebounded almost directly backwards. These large angle deflections were not consistent with Thomson's model.

From the above observations he concluded that large scattering angles could only occur if most of the mass of the atom, and all of its positive charge reside in a very small, extremely dense region called the atomic nucleus.

Thus Rutherford established a new model of the atom that was similar to the structure of planets in orbit around the sun. Rutherford's model consisted of a dense positive core at the center of the atom with electrons orbiting around it. This is called as Planetary Model of the atom.

Though Rutherford was successful enough to explain the rearrangement of the charged particles within the atom, his model faced some serious problems.

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