Evolution of Atomic Models


This image shows us evolution of atomic models from Dalton model to Thomson model to Rutherford model to Bohr model to Schrodinger model. Dalton model, the work of John Dalton, introduced the concept of atoms based on scientific observations and laws for the first time and provided a way to explain observations and laws such as the law of conservation of mass, the law of definite proportions and the law of multiple proportions. Dalton model considered atoms to be indivisible which came to be wrong as later discovery of electron by Sir Joseph John Thomson showed.


By discovery of electrons, Thomson model overthrew the idea of indivisible atoms factually and considered the first-discovered subatomic particle, electron and also presence of positive and negative charges in atoms. Thomson model considered the positive charge of atom to be diffuse all over atom which came to be wrong as later discovery of the nucleus by Ernest Rutherford showed.†


For the first time, Rutherford model introduced the existence of a nucleus, a tiny but heavy positively-charged central part, in atom based on the experimental results and provided the way for later discoveries and developments by giving a more accurate picture of atoms. Rutherford model couldnít justify the stability of atoms; also it had no explanation for electromagnetic spectrum of atoms already studied by scientists. These flaws showed that another model was needed.


For the first time, Bohr model considered quantized quantities in atoms by which calculation of energy levels and radii of shells in single-electron hydrogen atoms and explanation of the stability and electromagnetic spectrum of atoms became possible. However, Bohr model didnít consider the wave-like nature of electrons in atoms and it was inconsistent with uncertainty principle of Heisenberg. These problems were rectified by Schrodinger model. ††


For the first time, Schrodinger model included the wave-like nature of electrons in atoms beside the fact that it was supported by the Schrodinger equation, a significant landmark in the development of quantum mechanics, used for the study of quantum systems.




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