Atomic Model (old)

Thomson’s Atomic Model

Atom is a positive sphere with a number of electrons distributed within the sphere. It is also known as plum pudding model. It explains the neutrality of an atom. This model could not explain the results of Rutherford scattering experiment.

Rutherford’s Nuclear Model of Atom

It is based upon a-particle scattering experiment. Rutherford presented that

Most part of the atom is empty.
Atom possesses a highly dense, positively charged centre, called nucleus of the order 10-13 cm.
Entire mass of the atom is concentrated inside the nucleus.
Electrons revolve around the nucleus in circular orbits.
Electrons and the nucleus are held together by electrostatic forces of attraction.
Drawbacks of Rutherford’s Model

1. According to electromagnetic theory, when charged particles accelerated, they emit electromagnetic radiations, which CODIlE by electronic motion and thus orbit continue to shrink, so atom unstable. It doesn’t explain the stability of atom.

2. It doesn’t say anything about the electronic distribution electrons around nucleus.

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