JJ THOMSAN MODEL OF ATOM

It's PPT on Thomson model of atom for class 9. everything included in ppt is in textbook of science class 9.It is very easy to understand. Hope it help's you!

1. NAME : GAURI .V. SARDAL CLASS : 9 Y ROLL NO. : 36

2. Topic : - By gauri s

3. Dalton’s atomic theory suggested that atom was indivisible (which could not be broken down into smaller particles) . But the discovery of sub-atomic particles such as electrons & protons inside the atom disproved this postulate of Dalton’s atomic theory . The discovery of electrons and protons suggested that atoms are divisible.

4. Now the big question was : How these electrons & protons were arranged inside the atom? [Please note that the third subatomic particle (neutron) had not been discovered at that time ]

5. For explaining this, many scientists proposed various atomic models. J.J . Thomson was the first one to propose a model for the structure of an atom.

6. JOSEPH JHON THOMSON J.J. Thomson (1856- 1940), was born on 18 December 1856. He was awarded the Nobel prize in Physics in 1906 for his work on the discovery of electrons. He directed the Cavendish Laboratory at Cambridge for 35 years and seven of his research assistants subsequently won Nobel prizes.

7. J.J. Thomson , in 1904 proposed that : 1) An atom consists of a uniform sphere (or ball) of positive charges (due to presence of proton) with negatively charged electrons embedded in it . 2) The negative and positive charges are equal in magnitude, due to which an atom is electrically neutral. It has no overall positive or negative charge.

8. The colored area in sphere contains all positive charges in the atoms . The negatively charged electrons are spread throughout the positive charge. The total negative charge of electron is equal to the total positive charge of the sphere. This equal and opposite charges balance each other due to which an atom becomes electrically neutral on the whole.

9. J.J.Thomson’s Model of Atom Watermelon Negatively charged (electron) Spherical cloud of positively charge (proton) This model is been compared with a water melon in which seeds are embedded or with a pudding containing dry fruits.

10. It failed to explain how the positive charge holds on the electrons inside the atom . It failed to explain how protons and electrons were arranged in atom so close to each other. Although Thomson’s model of atom explained the electrically neutral nature of atom .

11. It also failed to explain an atom's stability. It was unable to explain the scattering experiment of Rutherford. So, it was rejected