1. Lewis Dot Diagrams for Covalent Molecules

2. 3 Types of Representations 1. Lewis structures of compound 2. molecular formula: H 2 3. structural formula: H-H [ - represents 1 pair of shared e - ]

3. Steps for drawing Lewis Dot diagrams for covalent molecules/compounds

4. Step 1: Step 1: arrange symbols –BINARY molecules are easy put next to each other H H H H

5. Step 2: count total # val e - each H has 1 val e - for total 2 val e -each H has 1 val e - for total 2 val e -

6. Step 3: distribute val e - around symbols H : H H : H

7. Step 4: test for validity must pass 2 tests: 1) total # dots must = total # val e - 1) total # dots must = total # val e - 2) 2) draw circles to show e - for each atom - every atom must have octet of e - (except H: needs 2) - bonding e - get counted twice - bonding e - get counted twice (once for each atom sharing them) (once for each atom sharing them)

8. Testing Lewis Diagrams H H : Test 1: 2 dots = 2 val e - Test 2: each H has 2 val e - ✔ ✔

9. Testing Lewis Diagrams F F Step 1 Step 2 (2)(7) = 14 valence electrons Step 3 F F ::........ Step 4 ✔..

10. Try HF H F Step 1 Step 2 7 + 1 = 8 valence electrons Step 3 H F : :.... Step 4 ✔

11. Types of Covalent Bonds single bond: –2 atoms share 1 pair of e - : double bond: – 2 atoms share 2 pairs of e - : : triple bond: – 2 atoms share 3 pairs of e - : : :

12. O O Step 1: Step 2: (2)(6) = 12 valence electrons Step 3: O O : ::...... Step 4: Test failed No Good! Try O 2 

13. 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 –double bond = 4 e - shared –triple bond = 6 e - shared

14. Try O 2 Again! O O Step 1: Step 2: (2)(6) =12 Step 3: distribute e - Step 3: distribute e - (single bond didn't work so try double bond) (single bond didn't work so try double bond) ::::::::........ Step 4: Test! ✔

15. 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! ..

16. Try N 2 with a double bond N N :: : :.. No Good! Step 4: Test 

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

18. Ternary Molecules more than 2 elements: - atom with lowest electronegativity placed in center - hydrogens always terminal (placed on outside)