1. Covalent Bonding – Lewis Dot Diagrams Packet pages 3-7

2. Representations of Molecules Lewis Structures of compound H 2 = Molecular Formula H-H = Structural Formula [- represents 1 pair of shared electrons ]

3. Halogens Share 1 pair (2 electrons): form single covalent bond

4. Single Bonds Hydrogen and Halogens for Single Bonds

5. Single bond = 2 electrons are shared

6. Double Bonds Oxygen and Sulfur

7. Double bond = ___ electrons shared 4

8. Triple Bonds

9. Triple bond = ___ electrons shared 6

10. Structure of Covalent Compounds NOT necessarily empirical - a lot are molecular….we can keep adding atoms! glucose lipids C 6 H 12 O 6 (fats)

11. STEPS for drawing Lewis Diagrams 1. Arrange symbols on paper the way think atoms are arranged - Diatomics easy – next to each other - Hydrogens always terminal (on outside) - Atom with least attraction (lowest electronegativity) for shared electrons placed in center H2H2 H2OH2O H H O H CO 2 O C O

12. Steps for drawing Lewis Diagrams 2. Add up # valence electrons all atoms H2H2 H2OH2O H H O H CO 2 O C O 2 816

13. Rules for drawing Lewis Diagrams start with single bonds (electron pairs) between all atoms 3. Distribute electrons, start with single bonds (electron pairs) between all atoms H2H2 H2OH2O H H O H CO 2 O C O 2 816

14. Rules for drawing Lewis Diagrams 4. Test validity (2 tests) 1.A) # dots = # valence electrons found in rule 2 2.B) Every atom has octet (except H – only wants 2) H2H2 H2OH2O H H O H CO 2 O C O 2 816 Bonding electrons get counted 2 times –once for each atom sharing them

15. Assessing Lewis Diagrams If dot structure passes both tests, you’re finished If fails one or both tests, try again If single bonds don’t work - try multiple bonds –Single bond = 2 electrons shared –Double bond = 4 electrons shared –Triple bond = 6 electrons shared

16. CO 2 O C O 16 CO 2 O C O 16 CHECK AGAIN 1.A) # dots = # valence electrons found in rule 2 2.B) Every atom has octet (except H – only wants 2)

17. O=C=O

18. Try some examples H 2, F 2, HF, O 2, N 2 Step 1: Draw symbols the way think atoms are arranged –Diatomics easy – atoms next to each other!

19. Drawing Lewis Diagrams H H Step 2: Count up the valence electrons valence electrons Each H has 1 valence electron so the total = 2 Step 3: Distribute the valence electrons, starting with single bonds between all atoms :

20. Testing Lewis Diagrams H H : Test 1: 2 dots in diagram = 2 valence electrons Test 2: Each H has 2 valence electrons (Remember H only wants 2)

21. Testing Lewis Diagrams F F Step 1 Step 2 2 X 7 = 14 valence electrons Step 3 F F : ::........

22. Try HF H F Step 1 Step 2 7 + 1 = 8 valence electrons Step 3 H F : :....

23. O O Step 1: Step 2: 2 X 6 = 12 valence electrons Step 3: O O : ::...... Step 4: Test failed No Good! Try O 2

24. Try O 2 Again! O O Step 1: Step 2: 2 X 6 =12 Step 3: Distribute electrons (single bond between atoms didn't work so try a double bond) ::........ Step 4: Test!

25. Try N 2 N N Step 1: Step 2: 2 X 5 = 10 electrons Step 3: Distribute electrons starting with a single bond between the nitrogen atoms :.. :.. : Step 4: Test No Good!

26. Try N 2 with a double bond N N :: : :.. No Good!

27. Try N 2 with a triple bond N N ::::: Step 4: Test