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 18th Century Europe
-Democritus
all matter is composed of small particles called atoms
Atomos - indivisible
18th 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 amu of O2, 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:
H2O and H2O2

7. Dalton’s Atomic Theory
All matter is made of indivisible & indestructible atoms.
All atoms of the same element are identical in their physical and chemical properties.
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 p. 78 #1-9
Be ready for the quiz next time!