1. Atomic Structure PSC Chapter 3

2. Atomic Theory of Matter Evidence of atoms Law of Definite Proportions Law of Conservation of Mass Law of Multiple Proportions Dalton’s Atomic Theory

3. Evidence of atoms 400 BC – Greeks Atomic Theory -Democritus all matter is composed of small particles called atoms Atomos - indivisible 18 th Century Europe – Experimental results support the existence of atoms

4. Basic Components of the Theory… Law of Definite Proportions – For any sample, a compound always has the same composition A given compound contains the same elems. in the same proportions by mass – For example: NaCl is always 39.34% Na and 60.66% Cl by mass

5. Basic Components of the Theory… Law of Conservation of Mass – For any chemical reaction, the mass of the products equals the mass of the reactants. Matter is neither created nor destroyed. – For example: 32.07 amu of S combines with 32.00 amu of O 2, 64.07 amu of sulfur dioxide.

6. Basic Components of the Theory… Law of Multiple Proportions – For any compounds formed by the same two elements, the mass ratio of one of the elems. that combines w/ a fixed mass of another elem. can be expressed in small whole numbers – For example: H 2 O and H 2 O 2

7. Dalton’s Atomic Theory 1. All matter is made of indivisible & indestructible atoms. 2. All atoms of the same element are identical in their physical and chemical properties. 3. Atoms of different elements differ in their physical & chemical properties

8. Dalton’s Atomic Theory 4. When atoms combine, they unite in simple, whole-number ratios to form compounds. 5. Chemical reactions consist of the combination, separation, or rearrangement of atoms.

9. Assignment Do Page 78 #1-9 Be ready for the quiz next time!