Thomson atomic theory model came into existence in the year 1903.
Thomson's atomic theory proposed a model of atom which is known as plum pudding model or Christmas pudding or chocolate chip cookie model. Till the end of the nineteenth century the concept of atom was similar to a small solid billiard ball. In the year 1897 Joseph john Thomson totally changed the view of an atom by discovering electron. Thomson’s atomic theory suggested that the atom is not indivisible as it was of smaller pieces – electrons and protons.
Thomson’s Atomic Theory proposed
1. An atom consists of a sphere of positive charge with negatively charged electron embedded in it
2. The positive and the negative charges in an atom are equal in magnitude, due to which an atom is electrically neutral. It has no over all negative or positive charge.
We can compare the Thomson’s atomic theory model with a water melon. The red edible part of a water melon represents the sphere of a positive charge where as the black seeds embedded in it is like the electrons.
Thomson discovered electron by the cathode ray tube. It has been previously seen that if a electric current is passed through a vacuum tube, a steam of glowing material was formed. Thomson found that the mysterious glowing stream would bend toward a positively charged electric plate. Thomson atomic theory proved that the stream is made up of small particles which is piece of the atom and is negatively charged. Thomson named these particles as electrons.
Thomson’s atomic theory model was compared to a Christmas pudding because it was seen that as the currants are embedded in the pudding similarly the negatively charged electrons was also embedded in the positively charged sphere. These negatively charged electron and positively charged proton make an atom neutral. For Thomson’s atomic theory model he was awarded noble prize in 1906 and he died in the year 1940.
