June 15, 2020
For educational institutions
Chem- atomic theory timeline
⟶ Updated 13 Sep 2017 ⟶
List of edits
1785 - Law of conservation of mass by LaVoisier.
1803 - Dalton's atomic theory.
1897 - JJ Thomson discovers the electron using modified cathode rays.
1904 - Hantuaro Nagoka represents the atom as a large, positively charged sphere with rings of negative electrons.
1911 - Ernest Rutherford designs an experiment to test the existing atomic model. He hypothesized that an atom has a positive nucleus surrounded by negative electrons.
1913 - Neils Bohr theorized electrons within an atom posses only certain discrete energies called energy levels.
1914 - Rutherford coined the word proton for the smallest unit of positive energy.
1932 - James Chadwick demonstrates that an atomic nuclei must contain heavy neutral particles and positive particles through his experiment.
1797 - The law of constant composition by Joseph Proust.
1900 - Max Planck suggests that radiation is quantized (it comes in discrete amounts).
1909 - Millikan measures the charge of the electron in his famous oil-drop experiment.
1923 - Louis de Broglie predicts the wave nature of electrons and suggested that all matter have wave properties.
1925 - The Schrodinger equation: to find the allowed energy levels of quantum mechanical systems.
1927 - Heisenberg Uncertainty Principle: the position and the velocity of an object cannot both be measured exactly at the same time.
460-370 BC? - Democritus proposed the idea of an atom and an atomic theory. He named the invisible particles atoms.
About & Feedback