Question :- Explain Rutherford Scattering Experiment .
Answers
Answer:
Rutherford's Alpha Scattering Experiment
Rutherford, in his experiment, directed high energy streams of α-particles from a radioactive source at a thin sheet (100 nm thickness) of gold. In order to study the deflection caused to the α-particles, he placed a fluorescent zinc sulphide screen around the thin gold foil.
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Answer :-
» From the results of Rutherford's Scattering Experiment, it was observed that :-
- most of the alpha - particles passed through the gold foil undeflected.
- a small fraction of the alpha - particles was deflected by small angles.
- a very few alpha - particles (≈ 1 in 20,000) bounced back, that is, were deflected by nearly 180°.
The results of this experiment were unexpected. According to Thomson model of atom, the mass of each gold atom in foil should have been spread evenly over the entire atom, and alpha - particles had enough energy to pass directly through such uniform distribution of mass. It was expected that the particles would slow down and change directions only by a small angles as they passed through the foil.
★ More to know :-
On the basis of above observations and conclusions, Rutherford proposed the nuclear model of atom (after discovery of protons). According to this model :
• The positive charge and most of the mass of the atom was densely concentrated in extremely small region. This very small portion of the atom was called nucleus by Rutherford.
• The nucleus is surrounded by electrons that move around the nucleus with very high speed in circular paths called orbits. Thus, Rutherford's model of atom resembles the solar system in which the nucleus plays the role of sun and the electrons that of revolving planets.
• Electrons and the nucleus are held together by electrostatic forces of attraction.