Chapter 3 Dalton
- 1. The Atom: From Philosophical Idea to Scientific Theory Laws of Chemistry developed in late 1700’s Dalton’s Atomic Theory Relating Dalton’s ideas to the new laws of chemistry
- 2. The world in the late 1700’s Revolutions eliminate monarchies Invention of metric system New belief that the natural world was understandable, rational, not only through faith, but through science Improved technology allows for better quantified data collection
- 3. Laws of Chemistry known by 1790 Law of Conservation of Mass Matter is neither created nor destroyed in chemical reactions. Law of Definite Proportions Compounds always have the same composition by mass, no matter the size of the sample Example: Salt is 39% sodium, 61% chlorine by mass, always! Law of Multiple proportions
- 4. Law of Multiple Proportions When 2 compounds are made of the same elements, comparisons of the masses of the elements in the compounds gives a small whole number ratio Text example on page 69, please follow! Compare CO to CO 2 ; even before we knew the formulas, we could figure out that one had exactly twice as much oxygen as the other
- 5. John Dalton, Chemist, Teacher Developed a theory that accounted for the newly discovered laws of chemistry. How is a theory different from a hypothesis?
- 6. John Dalton, 1808 Matter is made of small particles called atoms Atoms of one element are all alike. Atoms of different elements are different from each other.* Atoms can not be created or destroyed. ** Atoms combine in simple whole number ratios to form chemical compounds In reactions, elements are rearranged, not changed.
- 7. Updates to Dalton’s theory *Not all atoms of an element are identical in all properties! Ions have a charge, and different isotopes have different masses. **Atoms can be destroyed! They can not be destroyed through chemical means, but nuclear physicists dismember atoms using accelerators; atomic bombs split atoms, too
- 8. We still agree with most of Dalton’s statements. We agree that… All matter is made of atoms Atoms of a given element all have the same number of protons. A sample of an element has an average atomic mass and a density that are characteristic of that element. Atoms can not be subdivided, created or destroyed by chemical means. Atoms do combine in whole number ratios to form compounds. In reaction, elements are combined, separated or rearranged.
- 9. Validating Dalton’s Atomic theory with the Laws of chemistry The law of Conservation of Mass can be explained by Dalton’s assertion that atoms can not be destroyed, and that in chemical reactions, they are only rearranged The law of definite proportions can be explained by Dalton’s idea that atoms of a particular element always have the same properties, and will therefore always combine basically the same way The law of multiple proportions fits with Dalton’s idea that elements combine in simple whole number ratios
- 10. Homework due next time Read chapter 3 up to the end of Section 2 Page 71: Section Review 1-3 Page 76: #1, 3, 5 Page 90: #32