Chem- atomic theory timeline

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.