Notes: Lewis Dot Structures Part 2

1. Chemistry Boon Date: 09/10 & 09/07 2012 Notes: Lewis Dot Structures Part 2

2. Catalyst: Mystery Molecules Write the name of the molecule described: • This molecule consists of three atoms. Two of the atoms are of the same element. The molecule has two covalent bonds. This molecule makes up about 60% of a person’s body weight. It also covers about 70% of the earth. • This molecule consists of 24 atoms. This molecule is made of atoms of 3 elements. It is the product of photosynthesis and the reactant of cellular respiration.

3. Catalyst Answer 1 • Water! H2O

4. Catalyst Answer 2 • Glucose C6H12O6

5. Biology rewind: macromolecules • All organisms (living things) are made of macromolecules. • Macromolecules are covalent compounds. • The atoms in proteins, carbohydrates, nucleic acids, and lipids are all connected by covalent bonds.

6. Objectives • I can draw Lewis structures of molecules with single, double, or triple bonds. • I know that most biological compounds are formed by covalent bonds. • I can state that one mole is 6.02 x 1023 particles.

7. Agenda • Catalyst • HW Review • Lewis Dot Structures of Molecules Part 2 • Carbon Monoxide Reading Activity • Covalent Bonds Exit Slip • Demonstration: Intro to the Mole • Electron Configuration Practice

8. HW: Drawing Molecules WS • An electron in the outermost energy level of an atom that can participate in bonding is called a valence electron. • A structure in which atomic symbols represent nuclei and inner-shell electrons and in which dots are used to represent valence electrons is called a Lewis structure. • A possible Lewis structure of a molecule for which more than one Lewis structure can be written is called a resonance structure.

9. HW: Drawing Molecules WS • A covalent bond in which two atoms share two pairs of electrons is called a double bond. • A covalent bond in which two atoms share three pairs of electrons is called a triplebond. • A bond in which two atoms share one pair of electrons is called a single bond. • A nonbonding pair of electrons in the valence shell of an atom is called an unshared pair.

10. HW: Drawing Molecules WS 8. Methanol CH3OH 9. Propane C3H8

11. HW: Drawing Molecules WS 10. Water H2O 11. carbon monoxide CO

12. HW: Drawing Molecules WS 12. Nitryl fluoride NO2F 13. SO32-

13. HW Vocabulary Crossword • Down • Proton • Halogen • 4. Cation • Anion • Isotope • Electron configuration • Noble gas • Electronegativity • Valence electron • Mass number Across • Atomic mass • Atomic number • Ion • Period 13. Orbital 16. Nucleus 17. Crystal lattice • Octet rule • Alkali metal • Group

14. Chemistry Date: 09/10 & 09/11 2012 Notes: Lewis Dot Structures part 2

15. Lewis Dot Structures: Part 2 • In a covalent bond, atoms share electrons.

16. Lewis Dot Structures: Part 2 • A covalent bond in which two atoms share two pairs of electrons is called a double bond.

17. Lewis Dot Structures: Part 2 • A covalent bond in which two atoms share three pairs of electrons is called a triple bond.

18. Rules for covalent bonding • Each bond is made up of 2 electrons • Each atom wants to reach the same configuration as the noble gases • Duet rule: Hydrogen wants 2 valence electrons • Octet rule: All other atoms want 8 valence electrons • Atoms will share electrons with other atoms so that both get a full valence shell

19. Drawing Lewis Dots for Compounds CH4 • Steps: • 1. Draw Lewis Dot structures for the individual atoms • Double check your numbers of valence e- • 2. Put central atom in the center • 3. Put other atoms around • 4. Draw 2 dots between each pair • 5. Fill in other dots up to 8 (except for H) – if the atoms do not have enough valence electrons to reach 8, a double or triple bond is necessary. • 6. Replace all bonded pairs with lines Central atom H H C H H

20. Double and Triple Bonds • What happens when the total electrons do not match up with the Lewis structure? • Example: O2 • Draw the Lewis dot structure: Total valence electrons: O O O2 = 2 x 6 = 12 Single bonded structure uses too many electrons!

21. Lone pairs Double Bonds • If the structure has too many dots, remove lone pairs from two atoms and replace with a double bond • In a double bond, the atoms share 4 electrons • Replace the bonded pairs with 2 lines O O

22. O C O Double Bonds • Some atoms can have more than one double bond • Example: CO2 Total valence electrons: C = 4 O2 = 2 x 6 = 12 16

23. Practice • Carbon dioxide: CO2 • Carbon monoxide: CO • Sulfur dioxide: SO2 • Nitrogen gas: N2 • Dibromoethene: C2H2Br2 • Ethylene: C2H4

24. Agenda • Catalyst • HW Review • Lewis Dot Structures of Molecules Part 2 • Carbon Monoxide Reading Activity • Covalent Bonds Exit Slip • Demonstration: Intro to the Mole • Electron Configuration Practice

25. Carbon Monoxide Reading • Carbon monoxide is a very dangerous gas. This article provides vital information about this deadly gas. • Instructions: After each paragraph, ask yourself, “what did I just read?” and “why is this important?” If you cannot answer these questions, go back and reread the paragraph. • After reading, answer the questions at the bottom of the page.

26. Agenda • Catalyst • HW Review • Lewis Dot Structures of Molecules Part 2 • Carbon Monoxide Reading Activity • Covalent Bonds Exit Slip • Demonstration: Intro to the Mole • Electron Configuration Practice

27. Agenda • Catalyst • HW Review • Lewis Dot Structures of Molecules Part 2 • Carbon Monoxide Reading Activity • Covalent Bonds Exit Slip • Demonstration: Intro to the Mole • Electron Configuration Practice

28. Mole Demonstration… • The mole is a number we use to make counting atoms, ions, and molecules much easier. • One mole is the number of carbon atoms in 12 grams of carbon-12. • One mole is 6.022 x 1023 particles.

29. Homework • Due Wednesday 09.12: • Read textbook pp. 224-229 • Do problems: pp. 233 #1, 2, 4, 5, 6(a), 8(a) • Due Thursday or Friday 09.13 or 09.14: • Valence electron and ions review WS