PRESENTATION OUTLINE
460-320 BCE Democritus-Ancient Greek philosopher who was the first to propose an atomic universe.
1772 Antoine Lavoiser- Introduced the theory of combustion and the evolution of the concept of an element.
1789 Law of Conservation of Mass-States that matter can change from one form to another but it won't change its mass.
1803 John Dalton-Formed the Dalton Atomic Theory which were rules and laws about atoms.
1803 Dalton's Atomic Theory-1) all matter is made up of atoms. 2) atoms cannot be destroyed. 3) compounds are formed by combining different kinds of atoms. 4) a chemical reaction is a rearrangement of atoms.
1864 Dmitri Mendeleer-Formulated the periodic law, created his own version of the periodic table of elements, and predicted the properties of the next eight elements yet to be discovered.
1897 Plum Pudding Model-discovered by J.J. Thomson, protons and electrons are randomly spread throughout an atom.
1897 Cathode Ray Tube-vacuum tube containing electron guns and a fluorescent screen to view images.
1897 J.J Thomson-credited with the discovery of electons, he used cathode rays to find them. Also made the Plum Pudding Model.
1908 Robert Milikan-credited with discovering the charges on an atom.
1909 Ernest Rutherford-gold foil experiment and made first model of an atom with a nucleus.
1909 Gold Foil Experiment-Designed by Rutherford, he fired positively charged particles into a gold foil and every once in a while they would come back leading to the conclusion of a nucleus in an atom.
1913 Henry Mosley-contributed to chemistry by the chemical concept of the atomic number.
1913 Niels Bohr-developed the Bohr model of the atom which stated electrons have different levels.
1915 Bohr Planetary model-shows that protons are in the nucleus and electrons orbiting the nucleus are quantized.
1921 Erwin Shrodinger-developed a number if things on the quantum theory and formed the wave equation.
1925 Electron Cloud Model-electrons no longer move around the nucleus in a fixed pattern but rather in clouds.
1932 James Chadwick-credited with discovering the neutron.
