What is the purpose of having different models of atom

Thomson's model of atom was similar to a Christmas pudding. The electrons are scattered like currants in a sphere of positive charge that is the spherical Christmas pudding.

Watermelon is also a good example of the model of atom.Here positive charge is spread like the red part of watermelon while electrons are like the seeds that are studded to it.

Postulates :

1) Electrons are embedded in the sphere of positive charge.

2) The negative charge and positive charge cancel each other. Hence, the atom is neutral.

3) Mass of atom is due to electrons.

Limitations :

1)But Thomson's model could not explain the observations made by other scientists like Rutherford's who found out that there is a nucleus in a atom but Thomson's model didn't have any nucleus.

2) It didn't have any experimental support, Thomson just proposed the model.

RUTHERFORD'S MODEL OF ATOM

Rutherford's model of atom was similar to the solar system.The planets revolve around the Sun. Similarly, the electrons revolve around the nucleus. He called these electrons planetary electrons.

Postulates :

1) There is a positively charged,highly densed center in an atom, called nucleus.Almost, the whole mass of atom resides in the nucleus.

2) The electrons revolve around the nucleus in an arbitary manner.

3) The size of a nucleus is very small as compared to atom.A nucleus can be compared with a cricket ball in a cricket stadium which is the atom.

Limitations :

1) Any charged particle is expected to radiate energy when accelerated.To remain in the orbit the electron has to undergo acceleration,so it would radiate energy.

The electron after radiating energy will finally collapse into the nucleus.If this happens then matter would not exist;but matter exists so atoms are stable.

we can conclude that the melting point of table salt is above room temperature (it's actually 801 deg c). the melting point of mercury must be below room temperature (- 39 deg c).