2. electron shells a)Atomic number = number of Electrons Electrons are placed in shells according to rules: 1)The 1st shell can hold up to two electrons, and each shell thereafter can hold up to 8 electrons.

3. Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons C would like to N would like to O would like to Gain 4 electrons Gain 3 electrons Gain 2 electrons

5. Chemical bonds: an attempt to fill electron shells 1.Ionic bonds 2.Covalent bonds 3.Metallic bonds

6. Learning Check A. X would be the electron dot formula for 1) Na2) K3) Al B. X would be the electron dot formula 1) B2) N3) P

7. Lewis Structure, Octet Rule Guidelines When compounds are formed they tend to follow the Octet Rule. Octet Rule: Atoms will share electrons (e - ) until it is surrounded by eight valence electrons. Rules of the (VSEPR) game- i) O.R. works mostly for second period elements. Many exceptions especially with 3rd period elements (d-orbitals) ii) H prefers 2 e - (electron deficient) iii) :C:N::O::F: 4 unpaired 3unpaired2unpaired1 unpaired up = unpaired e- 4 bonds3 bonds2 bonds1 bond O=C=ON  NO = OF - F iv) H & F are terminal in the structural formula (Never central)........

8. IONIC BOND bond formed between two ions by the transfer of electrons

9. Formation of Ions from Metals Ionic compounds result when metals react with nonmetals Metals lose electrons to match the number of valence electrons of their nearest noble gas Positive ions form when the number of electrons are less than the number of protons Group 1 metals  ion 1+ Group 2 metals  ion 2+ Group 13 metals  ion 3+

10. Formation of Sodium Ion Sodium atom Sodium ion Na  – e   Na + 2-8-1 2-8 ( = Ne) 11 p + 11 p + 11 e - 10 e - 0 1 +

12. Anion (-) Cation (+)

13. Formation of Magnesium Ion Magnesium atom Magnesium ion  Mg  – 2e   Mg 2+ 12 p + 12 p + 12 e- 10 e - 0 2 +

14. Some Typical Ions with Positive Charges (Cations) Group 1Group 2Group 13 H + Mg 2+ Al 3+ Li + Ca 2+ Na + Sr 2+ K + Ba 2+

15. Learning Check A. Number of valence electrons in aluminum 1) 1 e - 2) 2 e - 3) 3 e - B. Change in electrons for octet 1) lose 3e - 2) gain 3 e - 3) gain 5 e - C.Ionic charge of aluminum 1) 3- 2) 5- 3) 3 +

16. Solution A. Number of valence electrons in aluminum 3) 3 e - B. Change in electrons for octet 1) lose 3e - C.Ionic charge of aluminum 3) 3 +

17. Learning Check Give the ionic charge for each of the following: A. 12 p + and 10 e - 1) 02) 2+3) 2- B. 50p + and 46 e- 1) 2+2) 4+3) 4- C. 15 p + and 18e- 2) 3+ 2) 3-3) 5-

18. Ions from Nonmetal Ions In ionic compounds, nonmetals in 15, 16, and 17 gain electrons from metals Nonmetal ionic charge: 3-, 2-, or 1-

19. Fluoride Ion unpaired electron octet     1 - : F  + e  : F :     9 p+ 9 p + 9 e- 10 e- 0 1 - ionic charge

20. Ionic Bond Between atoms of metals and nonmetals transfer of electrons Conductors and have high melting point. Examples; NaCl, CaCl 2, K 2 O

22. 1). Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.

24. COVALENT BOND bond formed by the sharing of electrons

25. Covalent Bond Between nonmetallic elements of similar electronegativity. Formed by sharing electron pairs Examples; O 2, CO 2, C 2 H 6, H 2 O, SiC

27. Bonds in all the polyatomic ions and diatomics are all covalent bonds Ex: NO 3 - CO 3 2-

28. when electrons are shared equally NONPOLAR COVALENT BONDS H 2 CO 2 Cl 2

29. 2. Covalent bonds- Two atoms share one or more pairs of outer-shell electrons. Oxygen Atom Oxygen Molecule (O 2 ) Oxygen Molecule (O 2 )

30. when electrons are shared but shared unequally POLAR COVALENT BONDS H 2 O NH 3

31. - water is a polar molecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.

32. METALLIC BOND bond found in metals; holds metal atoms together very strongly

33. Metallic Bond Formed between atoms of metallic elements Electron cloud, or sea of electrons around atoms Good conductors at all states, lustrous, very high melting points Examples; Na, Fe, Al, Au, Co

34. Ionic Bond, A Sea of Electrons

35. How to show how they formed It’s like a jigsaw puzzle. You put the pieces together to end up with the right formula.

36. Water H O Each hydrogen has 1 valence electron Each hydrogen wants 1 more The oxygen has 6 valence electrons The oxygen wants 2 more They share to make each other happy

37. Water Put the pieces together The first hydrogen is happy The oxygen still wants one more H O

38. Water The second hydrogen attaches Every atom has full energy levels Remember, the 1 st energy level is 2 H O H

39. Multiple Bonds Sometimes atoms share more than one pair of valence electrons. A double bond is when atoms share two pair (4) of electrons. A triple bond is when atoms share three pair (6) of electrons.

40. Carbon dioxide CO 2 - Carbon is central atom Carbon has 4 valence electrons Wants 4 more Oxygen has 6 valence electrons Wants 2 more O C

41. Carbon dioxide Attaching 1 oxygen leaves the oxygen 1 short and the carbon 3 short O C

42. Carbon dioxide l Attaching the second oxygen leaves both oxygen 1 short and the carbon 2 short O C O

43. Carbon dioxide l The only solution is to share more O C O

44. Carbon dioxide l The only solution is to share more O C O

45. Carbon dioxide l The only solution is to share more O CO

46. Carbon dioxide l The only solution is to share more O CO

47. Carbon dioxide l The only solution is to share more O CO

48. Carbon dioxide l The only solution is to share more O CO

49. Carbon dioxide l The only solution is to share more l Requires two double bonds l Each atom gets to count all the atoms in the bond O CO

50. Carbon dioxide l The only solution is to share more l Requires two double bonds l Each atom gets to count all the atoms in the bond O CO 8 valence electrons

51. Carbon dioxide l The only solution is to share more l Requires two double bonds l Each atom gets to count all the atoms in the bond O CO 8 valence electrons

52. Carbon dioxide l The only solution is to share more l Requires two double bonds l Each atom gets to count all the atoms in the bond O CO 8 valence electrons

53. How to draw them Add up all the valence electrons. Count up the total number of electrons that are being shared. For every pair draw a line. Fill in the rest of the valence electrons to fill atoms up.

54. Examples NH 3 N - has 5 valence electrons wants 8 H - has 1 valence electrons wants 2 N H

55. NHH H Examples Draw in the bonds All 8 electrons are accounted for Everything is full

56. N H H H Examples

57. HCN Put in single bonds Need 2 more bonds Must go between C and N NHC

58. HCN l Put in single bonds l Need 2 more bonds l Must go between C and N l Uses 8 electrons - 2 more to add NHC

59. HCN l Put in single bonds l Need 2 more bonds l Must go between C and N l Uses 8 electrons - 2 more to add l Must go on N to fill octet NHC … …

60. HCN NHC

61. Another way of indicating bonds Often use a line to indicate a bond Called a structural formula Each line is 2 valence electrons HHO HHO

62. Structural Examples H CN C O H H HCN H 2 CO