Describe thomson's model of an atom

Thomson Model of an atom

The description of Thomson’s atomic model is one of the many scientific models of the atom. It was proposed by J.J Thomson in the year 1904 just after the discovery of electrons. However, at that time the atomic nucleus was yet to be discovered. So, he proposed a model on the basis of known properties available at that time. The known properties are:

Atoms are neutrally charged

Negatively charged particles called electrons are present in an atom. Learn about Charged particles in Matter in more detail here.

Thomson’s Atomic Model- Postulates

According to the postulates of Thomson’s atomic model, an atom resembles a sphere of positive charge with electrons (negatively charged particles) present inside the sphere.

The positive and negative charge is equal in magnitude and therefore an atom has no charge as a whole and is electrically neutral.

Thomson’s atomic model resembles a spherical plum pudding as well as a watermelon. It resembles a plum pudding because the electrons in the model look like the dry fruits embedded in a sphere of positive charge just like a spherical plum pudding. The model has also been compared to a watermelon because the red edible part of a watermelon was compared to the sphere having a positive charge and the black seeds filling the watermelon looked similar to the electrons inside the sphere.
Limitations of Thomson’s Atomic Model

Thomson’s atomic model failed to explain how the positive charge holds on the electrons inside the atom. It also failed to explain an atom’s stability.

The theory did not mention anything about the nucleus of an atom.

It was unable to explain the scattering experiment of Rutherford.

Conclusion

Even though Thomson’s atomic model was inaccurate and had a few drawbacks, it provided the base for several other atomic structure models afterward. It is one of the foundation models that led to significant and revolutionary inventions later.