1. 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 Simplicity When atoms combine in only one ratio, "..it must be presumed to be a binary one, unless some cause appear to the contrary"

2. 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.

3. Synthesizing Water Vapor

4. Synthesizing Ammonia Gas

5. Synthesizing Carbon Dioxide

6. Equal Volumes of Gas Contain Equal Numbers of “Particles”

7. Problems Interpreti ng Combining Volume Data Assume Water’s Chemical Formula is HO

8. Assume Water’s Chemical Formula is H 2 O

9. The Answer! Amedeo Avogadro (1776 - 1856) Stanislao Cannizzario (1826 - 1910)

10. H2H2 O2O2 H2OH2O

11. 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)

12. Oxides of Carbon?

13. Berzelius’ Table of Atomic Weights (1814) ElementBased on O =100 Based on O = 16 Modern, Based on C-12 = 12 Hydrogen6.6361.0621.00794 Boron73.27311.72410.811 Carbon75.112.012.0107 Nitrogen79.5412.7214.0067 Oxygen1001615.9994 Fluorine60.09.6018.998403 Phosphorus167.51226.801930.973761 Sulfur201.0032.16032.065