Covalent Bonding

1. Chemistry Matter and Change Chapter 8 Covalent Bonding

2. Chapter 8 Main Idea Covalent bonds form when atoms share electrons.

3. Atoms gain stability when they share electrons and form covalent bonds. 8.1 Main Idea

4. Review Vocabulary & Concepts • Chemical bond • Valence electrons • Electronegativity • Lewis structure

5. New Vocabulary & Concepts • Covalent bond • Molecule • Sigma (σ)bond • Pi (π)bond • Endothermic reaction • Exothermic reaction • Single bond • Double bond • Triple bond

6. Why do Atoms Bond? • Sharing electrons takes less energy than being “alone” • Octet is usually the most stable electron configuration

7. What is a covalent bond? • Shared pairs of electrons • http://www.glencoe.com/sites/common_assets/science/cmc/cim/animations/ch8_3_1.swf

8. Single Covalent Bonds • Two atoms share one pair of electrons • Sigma bond (σ) • Either : or _ for a Lewis Structure ·+ · · · H H  H HorH-H

9. Multiple Covalent Bonds • Two atoms share more than one pair of electrons • One pair is a sigma bond (σ)the others are pi (π)bonds • Double bond shares 2 pair of electrons • Triple bond shares 3 pair of electrons

10. Comparing Bonds Sigma (σ) Bonds Pi (π) Bonds • Single • Centered • s orbital electrons • One pair of electrons is shared • Paired • Parallel • p orbital electrons • Multiple pairs of electrons are shared

11. Molecule • A neutral group of atoms joined together by covalent bonds.

12. Diatomic Molecules • Molecules made up of two atoms. • There are 7 diatomic molecules. • H2, N2, O2, F2, Cl2, Br2, I2

13. Diatomic Molecules • Br I N Cl H O F I couldn't exist without you! Oh, Ha Ha!

14. Hydrogen H· + ·H  H:H Hydrogen HydrogenHydrogen Atom Atom molecule • The hydrogen molecule has a single covalent bond. • The electronegativity of each hydrogenatom is the same, so the electrons are shared. Shared electron pair

15. Molecular Compounds • Compounds comprised of molecules.

17. Video • http://www.glencoe.com/sites/common_assets/science/cmc/cim/animations/ch8_1.swf

18. Lewis Structures and Octet • Practice by drawing • H2 • O2 • N2 • H2O • CO2 - + + -

19. Lewis Structures and Octet • Practice by drawing • H2 - + + -

20. Lewis Structures and Octet • Practice by drawing O2 σ - - - - - - - - - - - + - - - - - + + + - - - - - - - - π

21. Strength of Covalent Bonds • Strength depends on distance of the atoms from each other • With more bonds comes stronger bonds • O2 is stronger than H2 single bond < Double bond < Triple bond

22. Chemical Bonds

23. Chemical Bonds Electronegativity is an atom’s affinity for electrons. Differences in electronegativity dictate how electrons are distributed in covalent bonds. - nonpolar covalent bonds = equal sharing of electrons - polar covalent bonds = unequal sharing of electrons

24. Bonds and Energy • Endothermic reactions require additional energy for bonds to break • Exothermic reactions release energy when the bonds break (spontaneous)

25. Section 8.2 Chemistry Matter & Change Naming Molecules

26. Specific rules are used when naming binary molecular compounds, binary acids and oxyacids 8.2 Main Idea

27. objectives • Translate molecular formulas into binary molecular names. • Name acidic solutions.

28. Review Vocabulary & Concepts • Ionic bond • Covalent bond • Formula unit • Oxyanion • Naming ionic substances • Molecule

29. New Vocabulary & Concepts • Oxyacid • Binary acid

30. Naming Binary Molecular Compounds • Name the first element using the entire name of the element. • The second element in the formula is named using the root and suffix “-ide.” • Prefixes are used to indicate the numbers of each element.

31. Common Prefixes

32. Naming Binary Molecular Compounds • Exceptions to the rules: • The first element never uses “mono-” • There is an understood 1 if nothing is specified. • Awkward vowels can be dropped

33. Naming Binary Molecular Compounds Exception • The first element never uses “mono-” • There is an understood 1 if nothing is specified. • CO2 is carbon dioxide not monocarbon dioxide • CO is carbon monoxide, not monocarbon monoxide

34. Practice Naming Binary Compounds

35. Naming Binary Acids • The first word has the prefix “hydro-” followed by the root of the second element followed by “-ic” • The second word is “acid” • HCl- hydrochloric acid

36. Practice Naming Binary Acids • Hydrobromic acid • Hydrophosphic acid • Hydrosulfuric acid • HF • H2Se • HI

37. Naming Oxyacids • First word consists of the root of the oxyanion (with prefixes if needed) followed by a suffix as specified • If oxyanion ends in • The second word is always “acid.”

38. Naming Oxyacids

39. Naming Oxyacids • First word consists of the root of the oxyanion (with prefixes if needed) followed by a suffix as specified • The second word is always “acid.”

40. Look at the formula of the molecule Is it an acid? No Yes Is there oxygen present in the compound? Name the first element using a prefix if necessary Name the second element indicating the number of atoms and changing the suffix to –ide. Yes No Hydro(root) ic acid Root + -ic if the anion ends in –ate, or Root + -ous if the anion ends in –ite, then acid

41. Practice Naming Oxyacids

42. Can You • Translate molecular formulas into binary molecular names. • Name acidic solutions.

43. Section 8.3 Chemistry Matter & Change Molecular Structure

44. Structural formulas show the relative positions of atoms within a molecule. 8.3 Main Idea

45. objectives • List the basic steps used to draw Lewis structures. • Explain why resonance occurs and identify resonance structures. • Identify three exceptions to the octet rule and name molecules in which these exceptions occur.

46. Review Vocabulary & Concepts • Ionic bond • Covalent bond • Lewis-dot structure • Octet

47. New Vocabulary & Concepts • Structural formula • Resonance • Coordinate covalent bond • Space filling model • Ball and stick model

48. Molecular Structures • Many different ways to depict the same thing • Molecular formula • Structural formula • Lewis Structure • Space-filling model • Ball-and-stick model

49. Molecular Formula • Indicates number of each element in a molecule • H2O • C6H12O6 • NH3

50. Structural Formulas • Molecular model that shows the relative positions of the atoms O H H