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John Dalton•Elements Composed of indivisible atoms.•Atoms are alike for a given element.•Atoms for different elements differ in size, mass, etc.•Compounds are formed from two or more atoms of different elements.•Atoms combine is simple numerical ratios to form compounds.
Dalton’s Atomic Theory
Rule of Greatest SimplicityWhen atoms combine in only one ratio, "..it must be presumed to be a binary one,unless some cause appear to the contrary"
Law of Combining Volumes
Joseph Louis Gay-Lussac (1778 - 1850)
The ratio between the volumes of the reactant gases and the products can be expressed in simple whole numbers.
Synthesizing Water Vapor
Synthesizing Ammonia Gas
Synthesizing Carbon Dioxide
Equal Volumes of Gas Contain Equal Numbers of “Particles”
Problems Interpreting Combining Volume Data
Assume Water’s Chemical Formula is HO
Assume Water’s Chemical Formula is H2O
The Answer!Amedeo Avogadro (1776 - 1856)
Stanislao Cannizzario (1826 - 1910)
H2 O2 H2O
Meyer’s Reaction to Cannizzaro
It was as though the scales had been lifted from my eyes.
Doubt vanished and was replaced by a feeling of peaceful clarity.
Julius Lolthar von Meyer (1830 – 1895)
Oxides of Carbon?
Berzelius’ Table of Atomic Weights (1814)Element Based on O
=100Based on O = 16
Modern, Based on C-12 = 12
Hydrogen 6.636 1.062 1.00794
Boron 73.273 11.724 10.811
Carbon 75.1 12.0 12.0107
Nitrogen 79.54 12.72 14.0067
Oxygen 100 16 15.9994
Fluorine 60.0 9.60 18.998403
Phosphorus 167.512 26.8019 30.973761
Sulfur 201.00 32.160 32.065
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