John Dalton- 1803, 1805, 1808


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Who: Known as the father of modern atomic theory
Modern Atomic Theory: includes the elements the compose atoms

5 Parts to his theory:
1.    Elements are made of extremely small particles called atoms.
2.    Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.
3.    Atoms cannot be subdivided, created, or destroyed.
4.    Atoms of different elements combine in simple whole-number ratios to form chemical compounds.
5.    In chemical reactions, atoms are combined, separated, or rearranged.

About Dalton:
  •  Quaker in Cumberland England
  • Was a teacher and public lecturer
  • Moved to Manchester where he had more resources - so he pumped out his first paper about color blindness - called "Daltonism"

Dalton's View of Atomism:
  • Came to his view through meterology
  • He kept daily weather records from 1787 until his death (first book was Meteorological Observations)
  • Claimed that air was not a chemical solvent, but a mechanical system
  • Law of partial pressures: The pressure exerted by each gas in a mixture is independent of the pressure exerted by other gases, and where the total pressure is the sum of the pressures of each gas.
  • He proceeded to calculate atomic weights from percentage compositions of compounds, using an arbitrary system to determine the likely atomic structure of each compound. 
Picture: Elements and their combinations as described in John Dalton's New System of Chemical Philosophy
Solid Sphere Model