1. Topic: Covalent Bonding – Lewis Dot Diagrams Do Now: Identify Bond Type from Formula AuAg CO 2 Li 3 NNa 2 S Mg CsF H2OH2O NaCl SO 2 Cu CH 4 CovalentCovalent CovalentCovalentIonic IonicIonic Ionic Metallic Metallic Metallic Metallic

2. Covalent Molecule vs Ionic Compounds Electrons are shared Molecules are formed Electrons are transferred Ions form = crystal lattice

3. 3 representations of Molecules Molecular Formula –tells type and number of atoms –H 2 or O 2 Structural Formula –Shows bonds between atoms –H-H or O=O Lewis Dot Diagrams –Shows valence electrons shared between atoms

4. 3 types of bonds Single Bond – 2 shared valence electrons –When H or Halogens (F, Cl, I, Br) bond with other atoms (or eachother) they ALWAYS form Single Bonds

5. 3 types of bonds Single Bond – 2 shared valence electrons –When H or Halogens (F, Cl, I, Br) bond with other atoms or each other they ALWAYS form Single Bonds Double Bonds – 4 shared valence electrons

6. 3 types of bonds Single Bond – 2 shared valence electrons –When H or Halogens (F, Cl, I, Br) bond with other atoms or each other they ALWAYS form Single Bonds Double Bonds – 4 shared valence electrons Triple Bonds – 6 shared valence electrons

7. Bonding Capacity (# of bonds formed) 00 :Ne: Ne, Ar, Kr 22·O:O, S 33·N·N, P 44·C·C, Si 11·F:F, Cl, Br, I 11HH Bonding Capacity # Unpaired Electrons Lewis Structure Atom...... · ··

8. Bonding Capacity (# of bonds formed) 4 3 2 1

9. H2H2 H2OH2O CO 2 Draw these molecules on your paper…we are going to draw Lewis Dot Diagrams

10. Rules for drawing Lewis Diagrams 1. Arrange symbols on paper the way think atoms are arranged - Diatomics easy – next to each other - Hydrogens can never be in the middle, always on the outside - Atom with lowest electronegativity placed in center H2H2 H2OH2O H H O H CO 2 O C O

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

12. Rules for drawing Lewis Diagrams 3. Distribute electrons, start with single bonds (1 pair of electrons) between all atoms then fill in remaining H2H2 H2OH2O H H O H CO 2 O C O 2 816

13. Rules for drawing Lewis Diagrams 4. 2 tests 1.A) # dots = # valence electrons found in rule 2 2.B) Every atom has octet (8) (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

14. 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 – ALWAYS MOVE PAIR OF ELECTRONS between atoms

15. 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)

16. O=C=O

17. 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!

18. Drawing Lewis Diagrams H Step 2: Count up the 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 :

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

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

21. Try HF H F Step 1 Step 27 + 1 = 8 valence electrons Step 3 H F : :..

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

23. Try O 2 Again! 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!

24. Try N 2 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!

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

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