Structure of Atom

03 Thomson’s Model of The Atom

  • In 1897, J. J. Thomson discovered a negatively charged particle called electron which he assumed to be 2000 times lighter than a proton.
  • In his atomic structure model, he considered atoms to have a cloud of negative charge and the positive charges.
  • Along with Rutherford he was also the first to demonstrate the ionization of air by X-rays.
  • Thomson’s model of an atom is similar to plum pudding model or a watermelon.
  • He compared the red edible part of the watermelon to positively charged sphere whereas the seeds of watermelon to negatively charged particles.

Postulates of Thomson’s Atomic Model:

He proposed that

  • An atom consists of a positively charged sphere or ball with negatively charged electrons embedded in it.
  • The positive and negative charges in an atom are equal in magnitude.
  • So that the atom as a whole is electrically neutral. It has no overall positive or negative charge.

Limitations of Thomson’s Atomic Model:

The following are the drawbacks of Thomson’s atomic model:

  • The model of atom failed to explain how a positive charge holds the negatively charged electrons in an atom. So, it failed to explain the stability of an atom.
  • This theory also failed to account for the position of the nucleus in an atom.
  • Thomson’s model failed to explain the scattering of alpha particles.
  • Even though Thomson’s model was not an accurate to account for the atomic structure, it proved to be the base for the development of other atomic structure models.

Start your learning Journey !

Get SMS link to download the app