Thomson model: Introduction
In 1897, J.J.Thomson discovered a negatively charged particle known as an electron. Thomson discovered electron by cathode ray tube experiment. Cathode ray tube is a vacuum tube. Thomson assumed that an electron is two thousand times lighter than a proton and believed that an atom is made up of thousands of electrons having the negative charge. In this atomic structure model, he considered atoms to have a cloud of negative charge and the positive charges. He along with Rutherford 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.
Postulates of Thomson’s atomic model
- An atom consists of a positively charged sphere with electrons filled into it. The negative and positive charge present inside an atom are equal and as a whole, an atom is electrically neutral.
- Thomson’s model of the atom was compared to plum pudding and watermelon. He compared the red edible part of the watermelon to positively charged sphere whereas the seeds of watermelon to negatively charged particles.
Limitations of Thomson’s atomic model
- This model of atom failed to explain how a positive charge holds the negatively charged electrons in an atom.Therefore, 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.
Although Thomson’s model was not an accurate model to account for the atomic structure, it proved to be the base for the development of other atomic structure models. The study of the atom and its structure has paved the way for numerous inventions that have played a significant role in the development of humankind. To follow more about atomic models and quantum physics download Byju’s-the learning app.
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