1. Homework – Due Fri 12/17/10 Reread Sec 5.3 in your textbook. Copy the Section Summary on p 162. Answer Ques # 26-30, 33 on p 162

2. Reminders Turn in last week’s homework today if you did not already do so Completing this week’s homework will entitle you to a raffle ticket for Friday (in class raffle of a few miscellaneous items) There will probably be a quiz later this week - TBA Topics this week are: Valence electrons, electron dot diagrams, ions, ionic bonding

3. HAPPY MONDAY : ) 12-13-10 1. Cornell Notes 2. Practice Worksheet 3. Partner Practice

4. Why are electrons important? Electrons are responsible for HOW ELEMENTS REACT That is why we learned how to:  Write electron configurations  Draw electron orbital diagrams When we understand electrons  we can predict how elements will behave (what we can do with them)  Understand the structure of the periodic table

5. Valence Electrons The specific electrons responsible for the chemical properties of an element Electrons in an atoms outermost orbitals They are in the highest energy levels

6. Counting the Number of Valence Electrons 1. Write the electron configuration O 8 1s 2 2s 2 2p 4 2. Circle the subshells in the highest energy levels O 8 1s 2 2s 2 2p 4 3. Count the electrons in those orbitals O 8 1s 2 2s 2 2p 4 24 + = 6

7. Worksheet Example #1 How many valence electrons does Magnesium have? 1. Write the electron configuration 2. Circle the subshells in the highest energy level 3. Count the electrons in those orbitals Mg 12 1s 2 2s 2 2p 6 3s 2 2!

8. Worksheet Example #2 How many valence electrons does Chlorine have? 1. Write the electron configuration 2. Circle the subshells in the highest energy level 3. Count the electrons in those orbitals Cl 17 1s 2 2s 2 2p 6 3s 2 2 3p 5 5+= 7!

9. Electron Dot Structures Used to represent the valence electrons in an element 1. Draw the element SYMBOL 2. Dots representing electrons are placed around the four sides of the symbol one at a time Oxygen 6 valence electrons O

10. Example #3 What is the electron dot structure of Magnesium? What’s the symbol of magnesium? How many valence electrons? 2 Mg

11. Example #4 What is the electron dot structure of Chlorine? What’s the symbol of chlorine? How many valence electrons? 7 Cl

12. Example #5 What is the electron configuration of Fluorine? What is the electron dot structure of Fluorine? What do fluorine and chlorine have in common? What family are fluorine and chlorine in? 1s 2 2s 2 2p 5 FCl Same number of valence electrons! Halogens

13. Key Points Valence electrons are responsible for how elements react Elements in the same group have the SAME NUMBER OF VALENCE ELECTRONS – that’s why they have similar properties

14. Grab-It-Challenge You’ll be working on your own Select one activity card at a time Write down which activity card you select Complete the problems on the back of your worksheet When you are finished, have the teacher check it Once it’s correct, you can grab a new card Full credit = two cards done Bonus points for three or more cards