MAHE Manipal B.Sc Nursing 2025
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17 Questions around this concept.
An alpha nucleus of energy bombards a heavy nuclear target of charge Ze. Then the distance of the closest approach for the alpha nucleus with be proportional to
Rutherford's model of atom (I)
J.J Thomson's model - J. J. Thomson, who discovered the electron in 1897, proposed the plum pudding model of the atom in 1904 before the discovery of the atomic nucleus in order to include the electron in the atomic model. In Thomson’s model, the atom is composed of electrons surrounded by a soup of positive charge to balance the electrons’ negative charges, like negatively charged “plums” surrounded by positively charged “pudding”.
The Rutherford Model (Gold Foil Experiment ) :
Rutherford and his collegues Geiger and Marsden bombarded a thin gold foil of thickness approximately
In line with the plum pudding model, since the positive charge of atoms was evenly distributed and too small as compared to that of the alpha particles, the deflection of the particulate matter, if any, was predicted to be less than a small fraction of a degree.
Observations :
Conclusion: A highly concentrated positive charge at the center of an atom that caused an electrostatic repulsion of the particles strong enough to bounce them back to their source. The particles that got deflected by huge angles passed close to the said concentrated mass. Most of the particles passed undeviated as there was no obstruction to their path, proving that the majority of an atom is empty. Rutherford drew the conclusion that since the dense alpha particles could be deflected by the central core, it shows that almost the entire mass of the atom is concentrated there. Rutherford named it the “nucleaus” after performing the experiment in various gases.
Rutherford's model of atom (II)
Distance of closest approach :
The minimum distance from the nucleus up to which the
Impact parameter: It is defined as the perpendicular distance of the velocity of the alpha-particle from the centre of the nucleaus, when it is far away from the atom. The shape of the trajectory of the scattered alpha-particle depends on the impact parameter 'b' and the nature of the potential field. Rutherford deduced the following relationship between the impact parameter 'b' and the
scattering angle
Conclusion and drawback of Rutherford model:
Conclusion:
Limitations of Rutherford model:
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