1. Chemical Foundations: Elements, Atoms, and Ions Atoms & Compounds

2. Atoms and Compounds Objectives: Students will be able to identify 4 parts of Dalton’s Atomic Theory. Students will be able to write and interpret chemical compound formulas

3. Atoms and Compounds Important milestones in the development of modern atomic theory: Democritus (450 BC) Proposed that matter was not infinitely divisible Matter could be broken down into tiny particles he called atomos.

4. Atoms and Compounds Antoine Lavoisier (late 1700’s) Proposed the Law of Conservation of Matter Matter is not created or destroyed during chemical reactions Joseph Proust (1799) Proposed the Law of constant composition A given compound always contains the same elements in the same proportions by mass For example: the mass of water (H 2 O) always contains exactly 88.9% oxygen and 11.1% hydrogen.

5. Dalton’s Atomic Theory John Dalton – (early 1800’s) proposed the atomic theory of matter Mass of oxygen that combines with 1 gram of Carbon Compound 11.33 g Compound 22.66 g This can be explained in terms of atoms. Compound 1: CO (Carbon monoxide) Compound 2: CO2 (Carbon dioxide)

6. Dalton’s Atomic Theory Law of Multiple Proportions If 2 or more elements form a series of compounds, the ratios of the masses of elements can be reduced to small whole #’s

7. Dalton’s Atomic Theory Dalton’s Atomic Theory (early 1800’s) Elements are made up of tiny particles called atoms. Atoms of a given element are identical. Atoms of different elements are different in some fundamental way. Chemical compounds from when different elements combine. A given compound always contains the same elements in the same proportions. Chemical reactions involve reorganization of atoms. Atoms are not created or destroyed in chemical reactions.

8. Formulas of Compounds Compound-combination of two or more elements in a fixed proportion. H2OH2O Element Symbols # of H atoms Subscript of one is not included.