Atomic Model of Thomson | Plum Pudding Model | Limitations

In 1898, J. J. Thomson Proposed the first atom model. According to this model, an atom is a sphere having radius of the order of 10-10 m.

Here, we will discuss about Atomic Model of Thomson which is given by J. J. Thomson. So far, we have discussed about the Atoms, Atomic structure of elements and their properties.

Thomson's Atom Model

In 1898, J. J. Thomson proposed the first atom model. According to this model, an atom is a sphere having radius of the order of 10-10 m. The mass and the positive charge of the atom are uniformly distributed throughout the volume of the atom and the negatively charged electrons are embedded in it like seeds in a watermelon or plums in the pudding as shown in Fig. The total positive charge of atom is exactly equal to the total negative charge of electrons present in the atom so that the atom, as a whole, is electrically neutral.

Thomson atomic model
Thomson atomic model

At first, Thomson's plum pudding atom model appears to be a plausible model but subsequent studies in atoms showed that the distribution of the elections and positive charges are very different from that proposed in this model. The model suffers with the following limitations :

The discovery of subatomic particles led to the search how the subatomic particles are arranged in an atom. J. J. Thomson was the first and one of the many scientists who proposed models for the structure of an atom. J. J. Thomson discovered negatively charged particles by cathode ray tube experiment in the year 1897. This negatively particle is called electron. Thus, electron is discovered by sir J. J. Thomson.

Limitations

  1. Thomson's atom model could not explain the origin of the spectral lines of hydrogen atom.
  2. It could not account for large angle scattering of alpha particles as experimentally observed in Rutherford's alpha-particles scattering experiment.
  3. Thomson's atom cannot be stable.

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