Thomson's Model of Atom

Thomson’s model of the atom

In 1898, Sir J.J. Thomson postulated the following model of the atom.

(a) The atom consists of a cloud of +ve charge.

(b) The size of the +ve cloud is of the order of 10^-10 m.

(c) The electrons are embedded in the +ve cloud in the same way as the seeds are embedded in the water melon.

(d) Total +ve charge in the cloud is equal to the total –ve charge on the electrons.

(e) The electrons are distributed in the +ve cloud so as to provide stability to the system.

Drawbacks:

(a) Electrostatically, the model cannot be stable. Slight disturbance in the structure will set the electrons into oscillations and as a result energy should be radiated out of the atom as em waves.

(b) It cannot explain the origin of spectral lines observed in the spectrum of hydrogen and other atoms.

(c) It fails to explain the scattering of alpha-particles was observed by Rutherford.

            Because of these drawbacks, the Thomson’s model of the atom is rejected.

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