John Dalton (17661844), English chemist and physicist. A Croatian Jesuit who provided a prototype of the atomic theory. This theory explains what exactly is present inside the atom. Democritus was a Greek philosopher, 460 BC. Thomson who first discovered that the atom wasn’t indivisible after all. The atom would radiate a photon when an excited electron would jump down from a higher orbit to a lower orbit. This theory was first taking place in the year 1897 and later it was proposed by J.J Thomson in the year 1900. Niel Bohr’s Atomic Theory states that an atom is like a planetary model where electrons were situated in discretely energized orbits. Joseph John Thomson, was a British physicist and Nobel Laureate in Physics, who studied about the electric discharge tubes, got credited for the discovery of one of the sub-atomic particles that is Electron. In Thomson’s model, the atom is composed of electrons (which Thomson still called corpuscles, though G. Thomson and the other proposed by Ernest Rutherford Bohr’s model explains how electrons revolve. Thomson, who discovered the electron in 1897, proposed the plum pudding model of the atom in 1904 before the discovery of the atomic nucleus in order to include the electron in the atomic model. Two of these models, one is proposed by J.J. His model postulated that atoms consist of a big positively-charged sphere studded with negatively charged electrons (he called them 'corpuscles') like fruit in a plum pudding. Bohr model, description of the structure of atoms, especially that of hydrogen, proposed (1913) by the Danish physicist Niels Bohr.The Bohr model of the atom, a radical departure from earlier, classical descriptions, was the first that incorporated quantum theory and was the predecessor of wholly quantum-mechanical models. Thomsons model of the atom as a uniformly distributed substance. Formation of molecules combining with identical atomsĪtomic models were proposed to explain about the charged particles in an atom. Thomson proposed the 'plum pudding' theory of the divisible atom in 1904, after discovering electrons in 1897. In the Bohr model, which used quantum theory.Comparing the elements behavior with both the physical and chemical properties.The major problems before the scientists could recognize after the discovery of sub-atomic particles were: Observations and experiments mentioned by some scientists suggested that Dalton’s indivisible atom is composed of sub-atomic particles carrying positive charge and negative charge. In 1808 the first statement of a modern atomic theory was published by John Dalton, a Quaker schoolmaster from Manchester.