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History

History. Democritus - First to use the term atom Aristotle - Defined matter as composed of hot, cold, wet and dry John Dalton - Modern Atomic Theory and Law of Multiple Proportions Antoine Lavoisier - Law of conservation of mass Joseph Proust - Law of Definite Proportions

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History

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  1. History • Democritus - First to use the term atom • Aristotle - Defined matter as composed of hot, cold, wet and dry • John Dalton - Modern Atomic Theory and Law of Multiple Proportions • Antoine Lavoisier - Law of conservation of mass • Joseph Proust - Law of Definite Proportions • J.J. Thomson - Discovered the electron with cathode ray experiment and proposed Plum pudding model • Robert Millikan - Discovered the charge/mass of the electron using Oil Drop Experiment

  2. Ernest Rutherford - Discovered the nucleus using gold foil experiment • James Chadwick - Discovered the neutron • Henri Becquerel - discovered radiation emitted by Uranium • Marie Curie - discovered two other elements that emitted radiation (Polonium and Radium) • Niels Bohr - Proposed energy levels and the Planetary model of the Atom • Louis de Broglie - Proposed the wave particle duality of nature • Werner Heisenberg - Proposed the Uncertainty Principle • Erwin Schrodinger – Proposed electron cloud model (quantum mechanical model) of an atom

  3. John Newlands – noticed pattern when elements were arranged by atomic mass (repeated every 8th element). He used the word periodic to describe this pattern and named it the Law of Octaves • Lothar Meyer – made a connection between atomic mass and properties of elements and made periodic table • Dmitri Mendeleev– made a connection between atomic mass and properties of elements and made periodic table. Also predicted unknown elements. • Henry Mosely – arranged periodic table by atomic number and gave us Periodic Law

  4. Four parts of an experiment • Independent variable – what the scientist changes, what is being tested. • Dependent variable – what changes because of the independent variable. • Control – the comparison item, it is used to see if the independent has an effect (usually a sample with no independent used) • Constants – everything else that is in the experiment that we keep constant

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