2. Teacher Resources  Chapter 19 Color Teaching Transparency —Ch 19.2a Ch 19.2bCh 19.2aCh 19.2b  Laboratory Black line Masters Laboratory Black line Masters  Electronic Book Electronic Book  Skill Sheets

3. Chapter 19.2 Chemical Formulas CPO Science Integrated Physics & Chemistry

4. Developing A Model  Why is the periodic table of elements arranged this way?  Read Part 1 of the investigation

5. Developing A Model  What is an element’s oxidation number? —Electrons gained of lost to become a stable ion Atoms Valence Electrons Electron gained or lost during ionization Valence Electrons After Oxidation Number K Mg Al P Se Br Ar 11 lost8+1 22 lost8+2 3 3 lost8+3 53 gained8-3 62 gained 8 -2 71 gained8 80 gained 8 0

6. Key Questions  Why do atoms combine in certain ratios?  What role does oxidation numbers play?  How do you name compounds?

7. Developing An Experiment  What happens when a positive ion comes in contact with a negative ion? —Opposites attract —What charge does a Na ion have? How do you know? —What charge does a Cl ion have? How do you know? —Together they make? The compound NaCl

8. Run The Experiment  Tips  Complete the chart for part 2.  Make sure to use the the tiles.  Remember the oxidation numbers must add to zero

9. What did you learn?  What role do the oxidation numbers play in creating a compound?  Why didn’t lithium & argon create a compound?  What did you notice about the ratio of MgS? —It was the lowest ratio

10. Naming Compounds  These are the rules for ionic compounds.  Now name the compounds you created in part 2

11. Summary  What are oxidation numbers?  Why do atoms combine in certain ratios?  How do you name ionic compounds?