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John Dalton's Theory
Dalton's atomic theory is still valid in chemical thought, even though it has been a long time since it was formed. All matter is made of atoms. Atoms are indivisible and indestructible. Compounds are formed by a combination of two or more different kinds of atoms. John Dalton's experiments with gases that first became possible at the turn of the nineteenth century led John Dalton in 1803 to propose a modern theory of the atom. Matter is made up of atoms that are indivisible and indestructible. -
J.J Thomson's Theory
In 1897 the British physicist Joseph John or J. J.Thomson discovered the electron in a series of experiments designed to study the history of electric discharge in a high suction cathode-ray tube, an area being investigated by a lot of scientists at the time. Thomson was awarded the 1906 Nobel Prize in Physics for his work on the creation of electricity in gases. Seven of his students, including his son George Paget Thomson, also became Nobel Prize winners either in physics or in chemistry.