Rutherford scattering experiment involves the bombardment of thin foils with alpha particles. This results in the discovery of nucleus. Here, we will discuss about Rutherfords scattering experiment in structure of atom.
What is Rutherford’s scattering experiment
- Rutherford bombarded thin foil of metals like Au, Ag, Pt or Cu with fast moving alpha particles.
- Radium was the source of alpha rays placed in Pb block.
- ZnS screen observes the results.
What are the observations of Rutherford’s scattering experiment
- Most of the alpha particles (99.9%) went straight.
- Few alpha particles showed a deflection by a small angle.
- Very few alpha particles deflected by an angle of more than 90 degree
What are the conclusions of Rutherford’s scattering experiment
- Most of the rays went straight. Because there is sufficient empty space present in the atom.
- Few alpha particles showed deflection by a small angle. Because they passed very close to the positive body. Alpha particles are positively charged particles. Therefore, they showed a deflection by small angle.
- Alpha particles also deflected by an angle of more than 90 degree. It is due to head on collision of the same charged species.
- Very few alpha particles deflected by an angle of more than 90 degree. Because the positively charged body is present in a very very small volume.
- This small positively charged body is the of nucleus of atom.
Structure of Rutherford’s nuclear model of atom
- Nucleus is small positively charged centre where the entire mass of atom is present. But electrons have negligible mass. Nucleus consists of protons and neutrons. Neutrons are neutral and protons carry positive charge.
Nucleons = Protons + Neutrons
2. Extranuclear part is the space around the nucleus in which the electron revolves in a circular path.
Rutherford explained the stability of atom as electrons are revolving in a circular path around the nucleus. Therefore, centrifugal force balances the force of attraction.
Limitations of Rutherford’s nuclear model of atom
According to Maxwell’s electromagnetic theory, when a charged particle is revolving in a field of force, it loses energy continuously in the form of electromagnetic radiations. The orbit of the electron keeps on becoming smaller like a spiral path. And therefore, the electron should fall in to the nucleus. Hence, the atom should collapse. But, actually, atom is stable. Rutherford could not explain the stability of atom.
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