Hewitt/Lyons/Suchocki/Yeh Conceptual Integrated Science

1. Hewitt/Lyons/Suchocki/YehConceptual Integrated Science Chapter 12 THE NATURE OF CHEMICAL BONDS

2. This lecture will help you understand: • Electron Shells • The Ionic Bond • The Covalent Bond • Polar Bonds and Polar Molecules • Interparticle Attractions • Solutions • Solubility

3. Electron Shells • Atoms bond together through their electrons. To learn about bonding, therefore, we need to know something about how the electrons within an atom are organized.

4. Electron Shells • Atoms bond together through their electrons. To learn about bonding, therefore, we need to know something about how the electrons within an atom are organized. • Electrons behave as though they are contained within a series of seven concentric shells.

5. Electron Shells The numbers indicate the maximum number of electrons each shell may contain.

6. Electron Shells The numbers indicate the maximum number of electrons each shell may contain. Note: This is a “conceptual model” and not a representation of what an atom “looks like.”

7. Electron Shells The numbers indicate the maximum number of electrons each shell may contain. Note: Rather, it helps us to understand how the electrons within atoms behave.

8. The shells are more easily drawn in two dimensions.

9. The shells are more easily drawn in two dimensions. Each atom has its own configuration of electrons. Elements in the same group have similar configurations, which is why they have similar properties.

10. Electron Shells • Valence electrons: Electrons in the outermost shell of an atom. These are the ones that can participate in chemical bonding.

11. Electron Shells • Valence electrons: Electrons in the outermost shell of an atom. These are the ones that can participate in chemical bonding. • Electron-dot structure: A notation showing the valence electrons surrounding the atomic symbol.

12. Electron Shells • Valence electrons: Electrons in the outermost shell of an atom. These are the ones that can participate in chemical bonding. • Electron-dot structure: A notation showing the valence electrons surrounding the atomic symbol.

13. Special Note For heavier atoms, some valence electrons are more available than others. Krypton, for example, has 18 valence electrons, but only eight of these are typically shown within an electron-dot structure. These are the eight that extend farthest away from the nucleus. Kr

14. Electron Shells Note that elements within the same group have the same electron-dot structure.

15. Electron Shells CHECK YOUR NEIGHBOR Sodium, Na, atomic number 11, has only one valence electron. Upon losing this electron, what other atom in the periodic table does the sodium thus resemble? A. Neon, Ne, atomic number 10 • Magnesium, Mg, atomic number 12 • Lithium, Li, atomic number 3 • Sodium can only resemble sodium.

16. Electron Shells CHECK YOUR ANSWER Sodium, Na, atomic number 11, has only one valence electron. Upon losing this electron, what other atom in the periodic table does the sodium thus resemble? A. Neon, Ne, atomic number 10 • Magnesium, Mg, atomic number 12 • Lithium, Li, atomic number 3 • Sodium can only resemble sodium. Explanation: With 10 electrons, the sodium has enough electrons to fill the first and second shells, just like neon, Ne.

17. The Ionic Bond • Ion: An atom that has lost or gained one or more electrons.

18. The Ionic Bond • Ion: An atom that has lost or gained one or more electrons.

19. The Ionic Bond • Ion: An atom that has lost or gained one or more electrons. • Ionic Bond: The electrical force of attraction between oppositely charged ions.

20. The Ionic Bond • Ion: An atom that has lost or gained one or more electrons. • Ionic bond: The electrical force of attraction between oppositely charged ions. F− Na+

21. The Ionic Bond • Ion: An atom that has lost or gained one or more electrons. • Ionic bond: The electrical force of attraction between oppositely charged ions. • Molecular ion: Typically formed by the loss or gain of a hydrogen ion, H+.

22. The Ionic Bond H • Molecular ion: Typically formed by the loss or gain of a hydrogen ion, H+. H+ O H Water Hydrogen ion

23. The Ionic Bond H • Molecular ion: Typically formed by the loss or gain of a hydrogen ion, H+. H+ O H

24. The Ionic Bond H • Molecular ion: Typically formed by the loss or gain of a hydrogen ion, H+. H+ O H

25. The Ionic Bond H • Molecular ion: Typically formed by the loss or gain of a hydrogen ion, H+. O H+ H

26. The Ionic Bond H • Molecular ion: Typically formed by the loss or gain of a hydrogen ion, H+. + O H H The Ionic Bond Hydronium ion, H3O+

27. The Ionic Bond CHECK YOUR NEIGHBOR What is the chemical formula for a compound made of aluminum ions, Al3+, and oxygen ions, O2–? A. AlO • Al3O2 • Al2O3 • Al6O6

28. The Ionic Bond CHECK YOUR ANSWER What is the chemical formula for a compound made of aluminum ions, Al3+, and oxygen ions, O2–? A. AlO • Al3O2 • Al2O3 • Al6O6

29. The Ionic Bond CHECK YOUR NEIGHBOR What is the chemical formula for a compound made of magnesium ions, Mg2+, and oxygen ions, O2–? A. MgO • Mg2O2 • Mg4O4 • Any of the above

30. The Ionic Bond CHECK YOUR ANSWER What is the chemical formula for a compound made of magnesium ions, Mg2+, and oxygen ions, O2–? A. MgO • Mg2O2 • Mg4O4 • Any of the above Explanation: The chemical formula is used to show the ratio by which atoms combine. By convention, the lowest numbers are preferred, so 1:1 is used rather than 2:2. The numeral 1, however, is implied when no subscript is written.

31. The Covalent Bond • The type of electrical attraction in which atoms are held together by their mutual attraction for shared electrons.

32. The Covalent Bond • The type of electrical attraction in which atoms are held together by their mutual attraction for shared electrons. • There are two electrons within a single covalent bond.

33. The Covalent Bond • The type of electrical attraction in which atoms are held together by their mutual attraction for shared electrons. • There are two electrons within a single covalent bond. • The covalent bond is represented using a straight line.

34. The Covalent Bond • The type of electrical attraction in which atoms are held together by their mutual attraction for shared electrons. • There are two electrons within a single covalent bond. • The covalent bond is represented using a straight line. F F F — F

35. The Covalent Bond • The number of covalent bonds an atom can form equals its number of unpaired valence electrons.

36. The Covalent Bond • The number of covalent bonds an atom can form equals its number of unpaired valence electrons.

37. The Covalent Bond • The number of covalent bonds an atom can form equals its number of unpaired valence electrons.

38. The Covalent Bond • The number of covalent bonds an atom can form equals its number of unpaired valence electrons.

39. The Covalent Bond • The number of covalent bonds an atom can form equals its number of unpaired valence electrons. • Multiple covalent bonds are possible.

40. The Covalent Bond • The number of covalent bonds an atom can form equals its number of unpaired valence electrons. • Multiple covalent bonds are possible.

41. Polar Bonds and Polar Molecules • Electrons within a covalent bond are shared evenly when the two atoms are the same.

42. Polar Bonds and Polar Molecules • Electrons within a covalent bond are shared evenly when the two atoms are the same. • They may be shared unevenly, however, when the bonded atoms are different.

43. Polar Bonds and Polar Molecules • Electrons within a covalent bond are shared evenly when the two atoms are the same. • They may be shared unevenly, however, when the bonded atoms are different. • Electronegativity: The ability of a bonded atom to pull on shared electrons. Greater electronegativity means greater “pulling power.”

44. Polar Bonds and Polar Molecules • Electronegativity: The ability of a bonded atom to pull on shared electrons. Greater electronegativity means greater “pulling power.” High Low

45. Polar Bonds and Polar Molecules • Electronegativity: The ability of a bonded atom to pull on shared electrons. Greater electronegativity means greater “pulling power”.

46. Polar Bonds and Polar Molecules • But if polar bonds within a molecule are facing in equal and opposite directions…

47. Polar Bonds and Polar Molecules • But if polar bonds within a molecule are facing in equal and opposite directions… …then the polarity may cancel itself out.

48. Polar Bonds and Polar Molecules • But if polar bonds within a molecule are facing in equal and opposite directions… …then the polarity may cancel itself out. …or not!

49. Polar Bonds and Polar Molecules

50. Polar Bonds and Polar Molecules CHECK YOUR NEIGHBOR Which is heavier: carbon dioxide, CO2, or water, H2O? A. Carbon dioxide is heavier. • Water is heavier. • They both have the same number of atoms so they weigh the same. • It depends.