Chemistry Honors: Ch. 1
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16 terms
Terms | Definitions |
|---|---|
 400 B.C. | Demokritos and Leucippos use the terms "atomos" |
| Time of Alchemy | 2000 years |
| 1500s | Georg Bauer: systematic metallurgy Paracelsus: medicinal application of minerals |
| 1600s | Robert Boyle: The Skeptical Chemist. Quantitative experimentation, identification or elements |
| 1700s | Georg Stahl: Phlogiston Theory Joseph Priestly: Discovery of O2 Antoine Lavoisier: The role of O2 in combustion, law of conservation of mass, first modern chemistry textbook |
| 1800s | Joseph Proust: law of definite proportion (composition) John Dalton: the atomic theory, the law of multiple proportions Joseph Gay-Lussac: combining volumes of gases, existence of diatomic molecules Amadeo Avogadro: molar volumes of gases Jons Jakob Berzelius: relative atomic masses, modern symbols for the elements Dmitri Mendeleyev: the periodic table J.J. Thomson: discovery of the electron Henri Becquerel: discovery of radioactivity |
| 1900s | Robert Millikan: charge and mass of the electron Ernest Rutherford: existence of the nucleus, and its relative size Meitner & Fermi: sustained nuclear fission Ernest Lawrence: the cyclotron and trans-uranium elements |
| Dalton's Atomic Theory (1808) | All matter is composed of extremely small particles called atoms Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties Atoms cannot be subdivided, created, or destroyed Atoms of different elements combine in simple whole-number ratios to form chemical compounds In chemical reactions, atoms are combined separated of rearranged |
| Modern Atomic Theory | Several changes have been made to Dalton's theory. Dalton: atoms of a given element...and other properties Modern #1: atoms of an element have a characteristic average madd which is unique to that element Dalton: atoms cannot be subdivided...destroyed Modern #2: atoms cannot be subdivided, created, or destroyed in ordinary chemical reactions. However, these changes CAN occur in nuclear reactions |
| Discovery of the Electron | 1897; J.J. Thomson used a cathode ray tube to deduce the presence of a negatively charged particle |
| Cathode Ray | cathode ray tubes pass high voltage electricity through a gas that is contained at a very low pressure. When particles pass through, they slit and (-) is drawn to (+) plate, while (+) is drawn to (-) plate. have identical properties regardless of the element (gas) used to produce them. all elements must contain identically charged electrons |
| Thomson's Atomic Model | J.J. Thomson believed that the electrons were like plums embedded in a positively charged "pudding" thus it was called the "plum pudding" model |
| Mass of the Electron | 1909; Robert Millikan determines the mass of the electron with the oil drop apparatus. |
| Oil Drop Apparatus | see ppt |
| Conclusions from the Study of the Electron | cathode rays have identical properties regardless of the element used to produce them. All the elements must contain identically charged electrons atoms are neutral, so there must be positive particles in the atom to balance the negative charge of the electrons electrons have so little mass that atoms must contain other particles that account for most of the mass |
| Gold Foil Experiment | Rutherford: alpha particles are helium nuclei. particles were fired at a thin sheet of gold foil. particle hits on the detecting screen (film) are recorded |
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