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प्रश्न
Describe the Rutherford's model of an atom. State one drawback of Rutherford's model of the atom.
उत्तर
(a) Rutherford's model of atom-
Ernest Rutherford was interested in knowing how the electrons are arranged within an atom. He conducted an experiment in which a thin gold foil was bombarded with fast moving alpha (α) particles.
• He selected a gold foil because he wanted a layer as thin as possible. The gold foil was about 1000 atoms thick.
• The particles used for bombarding the gold foil were doubly-charged helium ions. Since, they have a mass of 4 u, the fast-moving α particles have a considerable amount of energy.
• It was expected that α particles would be deflected by the sub-atomic particles in the gold atoms. Since, the α particles were much heavier than the protons, he did not expect to see large deflections.
But the α particle scattering experiment produced totally unexpected results.
The following observations were made:
(i) Most of the fast moving α-particles passed straight through the gold foil.
(ii) Some of the α-particles were deflected by the foil by small angles.
(iii) Surprisingly, one out of every 12000 particles appeared to rebound.
Conclusions:
(i) The first observation led to the conclusion that most of the atom is hollow.
(ii) The small angle deviation of the α particles confirms the presence of a positively charged centre called nucleus.
(iii) The third observation confirms that the nucleus of an atom is solid as the ray returns on its path and is very small in size because 1 out of 12000 rays returns.
Drawbacks of Rutherford’s model of the atom :
The major drawback of Rutherford’s model is that it does not explain the stability of an atom. The orbital revolution of an electron is not expected to be stable. Any particle in a circular orbit would undergo acceleration. During acceleration, charged particles would radiate energy. Thus, the revolving electron would lose energy and finally fall into the nucleus. If this were so, the atom should be highly unstable. Therefore, matter would not exist in the form that we know. However, we know that atoms are stable. So, this model could not explain this reasoning.
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संबंधित प्रश्न
State whether the following statement is true or false :
Thomson proposed that the nucleus of an atom contains protons and neutrons.
(a) What is the nucleus of an atom and what is the nature of charge on it?
(b) Name the scientist who discovered the nucleus of atom.
Why did Rutherford select a gold foil in his α–ray scattering experiment?
In what way is the Rutherford’s atomic model different from that of Thomson’s atomic model?
Higher-Order Thinking skills: (HOTS)
In Rutherford's experiment of scattering alpha particles, can we take a foil of any other metal instead of gold?
Higher-Order Thinking skills: (HOTS)
How Rutherford’s model is different from that proposed by J.J. Thomson?
Gold foil alpha particle scattering experiment was performed by ______.
In Rutherford’s experiment, the bouncing of alpha particles suggests that the nucleus of an atom is negatively charged.
When an α-particle happens to come near a nucleus the intense electric field of these scatters it through a large angle then what is the effect of atomic electrons on α-particle?
The Rutherford α-particle experiment shows that most of the α-particles pass through almost unscattered. While some are scattered through large angles. What information does it give about the structure of the atom?
