Chemistry I Chapter 9

1. Chemistry I Chapter 9 Covalent Bonding

2. Why do atoms bond? 1. Atoms bond to become more stable. 2. A full valence shell is the most stable configuration 3. In an ionic bond, atoms gain or lose electrons. 4. In covalent bonds, atoms share electrons so that each atom has a full valence shell.

3. Why do atoms bond? • Covalent bonds usually happen between element s that are close to each other on the periodic table.

4. Why do atoms bond? • Covalent bonds usually happen between element s that are close to each other on the periodic table. • Most covalent bonds are between nonmetals.

5. Why do atoms bond? • Covalent bonds usually happen between element s that are close to each other on the periodic table. • Most covalent bonds are between nonmetals. • A molecule is formed when two or more atoms bond covalently.

6. Why do atoms bond? 5. Covalent bonds usually happen between element s that are close to each other on the periodic table. 6. Most covalent bonds are between nonmetals. 7. A molecule is formed when two or more atoms bond covalently.

7. Why do atoms bond? 8. There are 7 elements that always exist as diatomic molecules. Diatomic molecules do not exist as single atoms but as molecules of the atoms bonded together. 9. The 7 diatomic molecules are • H2 O2 N2 • F2 Cl2 Br2 I2

8. 10. Draw the lewis structure of the 7 diatomic molecules.

9. Why do atoms bond? 11.These seven molecules exist as diatomic molecules because by sharing electrons each can have a full valence shell.

10. Why do atoms bond? • The electrons that are shared or the shared pairs are called the bonding electrons.

11. Why do atoms bond? 12. The electrons that are shared or the shared pairs are called the bonding electrons. 13.The electrons that belong to individual atoms are called unshared pairs.

12. 14. Draw Lewis structures for the following molecules: • H2O • NH3 • CH4 • HBr • PH3 • CCl4 • SiH4 • HCl

13. Why do atoms bond? 15.Unshared pairs are shown with two dots. Shared pairs are shown with a dash. 16.Usually the element furthest to the left on the periodic table is in the middle.

14. Why do atoms bond? 17. Hydrogen is always on an end because it only makes one bond. 18.Single covalent bonds are formed when a single pair of electrons are shared.

15. Why do atoms bond? 19.Single bonds are also called sigma bonds. The greek letter sigma is writtenσ. 20. In a sigma bond, the valence orbitalsoverlap each other. Sigma bonds happen with s and p orbitals.

16. Multiple Bonds • 21. Double and triple bonds are multiple covalent bonds. 22. A double bond occurs whenever atoms need to share twopairs of electrons so that each atom has a full valence shell.

17. 23. Draw the Lewis structures for the following molecules: • O2 • C2H4 • CO2

18. Multiple Bonds • 24. When atoms have multiple bonds a pi bond forms (π bonds). The pi bond is found above and below the line where the atoms are connected.

19. Multiple Bonds 25.A double bond has one sigma bond and one pi bond. 26.A triple bond has one sigma bond and two pi bonds.

20. Strength of Covalent bonds 27. The strength of the bonds depends on how close the atoms nuclei are. 28.The shorter the bond the stronger the bond.

21. Strength of Covalent bonds 29.As the number of shared pairs increases the length decreases.

22. Strength of Covalent bonds • Single bonds are the longest • Double bonds are in the middle • Triple bonds are the shortest.

23. Strength of Covalent bonds 30.The amount of energy needed to break a specific covalent bond is called the bond dissociation energy.

24. Strength of Covalent bonds 31.Bond dissociation energy is always positive.

25. Strength of Covalent bonds • For example Molecule bond length dissociation energy F2 1.43 X 10-10m 159 kJ/mol O2 1.21 x 10-10m 498 KJ/mol N2 1.10 X 10-10 m945 KJ/mol

26. Multiple bonds 32.The chemical potential energy of a molecule is the sum of the bond dissociation energies for all bonds in a molecule

27. Multiple bonds 33.Endothermic reactions occur when it takes more energy to break the bond than is released when the new bonds form. • Endothermic – energy is absorbed.

28. Multiple bonds 34.Exothermic reactions occur when more energy is released when the new bond forms than was needed to break the original bonds. • Exothermic – energy is released.

29. Section 2 Naming Binary Molecular Compounds. 35. Binary molecular compounds contain only two different elements both of which are nonmetals.

30. Section 2 36.Naming Binary Molecular Compounds. • Naming rules 1. The first element is named using the entire first element name 2.The second element is named using the root word with the suffix – ide added.

31. Section 2 36.Naming Binary Molecular Compounds. • Naming rules 3. Prefixes are used to indicate the number of atoms of each element present. The exception is that the first element in the formula never uses the prefix mono.

32. Section 2 37.Naming Binary Molecular Compounds. • # ATOMS/ PREFIX • 1 - MONO2 - DI 3 - Tri 4 - Tetra 5 - Penta

33. Section 2 Naming Binary Molecular Compounds. • # ATOMS/ PREFIX • 6 -Hexa • 7 - Hepta • 8 - Octa • 9 -Nona • 10 - Deca

34. 38. Name the following molecular compounds • P2O5 • CCl4 • As2O3 • CO • SO2 • NF3

35. 39. Common names of molecular compounds H2O water Dihydrogen Monoxide NH3 ammonia Nitrogen Trihydride N2O laughing gas Dinitrogen monoxide

36. Naming Acids 40. All acids have hydrogen as the cation. 41. Acids are molecules that separate into ions in water. 42. The two types of acids are binary and oxyacids.

37. Binary Acids 43. All binary acids have hydrogen and one other element Examples HCl H2S

38. Naming Binary Acids 44. Use the prefix hydro, the root name with the ending changed to –ic • HCl _____________ • HBr _____________ • HF ______________ • H3P _____________

39. Naming Binary Acids • All acids that have a polyatomic ion that does not contain oxygen will use the above rules • HCN _____________

40. Naming Oxyacids 45. Any acid that contains hydrogen and an oxyanion is an oxyacid.

41. Rules for naming oxyacids 46.The name of the acid has the name of the polyatomic ion, a suffix and the word acid. • If the polyatomic ion ends in –ate , change the ending to –ic. • If the polyatomic ion ends in – ite, change the ending to -ous

42. Rules for naming oxyacids • H2SO4 _______________ • H2SO3 _______________ • HNO3 _______________ • HNO2 _______________

43. Name the following acids ( some are binary and some are oxyacid) • HI _______________ • HClO3 _______________ • HClO2_______________ • H2SO4 _______________ • H2S __________________

44. 47. Flow Diagram for all molecular compounds

45. Section 3Molecular Structural Models 48. There are five different kinds of molecular structures use to show the 3 dimensional arrangement of molecules.

46. Section 3Molecular Structural Models • A.) molecular formula • The symbols can be arranged to show how the atoms are grouped. • i.e., HC2H3O2

47. Section 3Molecular Structural Models • B.) Structural formulas- • Uses dashes but does not show unshared pairs of electrons.

48. Section 3Molecular Structural Models • C.) Lewis Structures- • Uses dashes to show bonds and dots to show unshared pairs.

49. Section 3Molecular Structural Models • D.) Space filling- different elements are represented by different colors. Atoms are stuck together like marshmallows glued together.

50. Section 3Molecular Structural Models • E.) Ball and stick- • Balls represent the atoms and the sticks represent the bonds.