1 Unit 6: Bonding Kristen L. Hewitt

2 Unit 6: Bonding Chemical Bonds are the forces that hold compounds together: Energy must be added in order to break a bond (overcome the attraction) ENDOTHERMIC Energy is released when a new bond is formed (because the opposite must be true)EXOTHERMIC

3 Unit 6: Bonding When two chemicals react to form new products, some bonds are broken and new bonds are formed the new compounds are very stable and have less energy than the original molecules - and energy is released!!

4 Unit 6: Bonding If energy must be added, it is listed on the REACTANTS side ENDOTHERMIC If energy is released, it is listed on the PRODUCTS side EXOTHERMIC

5 Unit 6: Bonding The energy that is released is yielded as heat or light energy… To take a closer look, let’s examine the burning of methane

6 Unit 6: Bonding Endothermic pg 196

7 Unit 6: Bonding Exothermic pg 196

8 Unit 6: Bonding Overall, more energy comes form creating new bonds then the breaking of old bonds, and energy is released...

9 Unit 6: Bonding In general, if a particular reaction is exothermic, and produces energy overall, then to reverse the reaction, you would have to add the energy back in, making the reverse reaction endothermic

10 Unit 6: Bonding

11 Unit 6: Bonding Valence electrons Electrons in the highest principal energy levels are the electrons that can be used for bonding 3arranged around the symbol of the element to easily identify bonding electrons 3this symbol arrangement is called the Lewis Dot Structure

12 Unit 6: Bonding Chemical Bonding How do you know which bond will form and how is this drawn?

13 Unit 6: Bonding Chemical Bonding How do you know which bond will form and how is this drawn? Lewis Dot Structures

14 Unit 6: Bonding Chemical Bonding How do you know which bond will form and how is this drawn? Lewis Dot Structures: H

15 Unit 6: Bonding Chemical Bonding How do you know which bond will form and how is this drawn? Lewis Dot Structures: H

16 Unit 6: Bonding Chemical Bonding How do you know which bond will form and how is this drawn? Lewis Dot Structures: H *Now ask yourself what kind of atom, or atoms do you have?

17 Unit 6: Bonding Chemical Bonding If electrons are lost and gained IONS are formed IONIC BONDS are created due to the attraction between the positive and negative ion

18 Unit 6: Bonding Chemical Bonding If electrons are lost and gained IONS are formed IONIC BONDS are created due to the attraction between the positive and negative ion METAL + NONMETAL Na+ Cl-

19 Unit 6: Bonding Chemical Bonding If an atom cannot lose or gain, and decides to SHARE its electrons instead a different bond is formed… COVALENT bond NONMETAL + NONMETAL CH4

20 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: Na Cl

21 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: Na --> Na Cl --> Cl

22 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: Na --> Na Ask yourself, ionic or covalent? Cl --> Cl

23 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: Na --> Na Metal and nonmetal, IONIC, electrons are Cl --> Cltransferred

24 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: Na Cl Na goes back to previous shell which is full (like Ne) and Cl gets a full shell (like Ar)

25 Unit 6: Bonding A.5 - Chemical Bonding Lewis Dot Structures: Na Cl Na goes back to previous shell which is full (like Ne) and Cl gets a full shell (like Ar)

26 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: Mg Cl

27 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: Mg --> Mg Cl --> Cl

28 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: Mg --> Mg Ask yourself, ionic or covalent? Cl --> Cl

29 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: Mg --> Mg Metal and nonmetal, IONIC, electrons are Cl --> Cltransferred

30 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: Mg Cl Mg goes back to Na and Cl gets a full shell (like Ar)

31 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: Mg Cl What happens to extra electron on Mg?

32 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: ClMg Cl Need another Cl!! Remember your criss-cross rules!!

33 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: _ 2 _ Cl Mg Cl

34 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: C --> H -->

35 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: C --> C H --> H

36 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: C --> C Ask yourself, ionic or covalent? H --> H

37 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: C --> C Two nonmetals = Covalent H --> H

38 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: C --> C Two nonmetals = Covalent H --> HHow many hydrogens do I need to get an octet for carbon?

39 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: HOrganic molecules H C Halways forms the Hfour bonds around carbon!!

40 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: CH 3 Cl C  C Cl  Cl H  H

41 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: CH 3 Cl C  C Cl  Cl H  H

42 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: CH 3 Cl C  C Cl Cl  ClC H  HH H H

43 Unit 6: Bonding Chemical Bonding Lewis Dot Structures: CH 3 Cl C  C Cl Cl  Cl H C H H  HH

44 Unit 6: Bonding Chemical Bonding  sharing of 1 pair of electrons creates a single bond  sharing of 2 pairs of electrons creates a double bond  sharing of 3 pairs of electrons creates a triple bond

45 Unit 6: Bonding Chemical Bonding  sharing of 1 pair of electrons creates a single bond H ◦◦ H  sharing of 2 pairs of electrons creates a double bond :O : : O :  sharing of 3 pairs of electrons creates a triple bond : N : : : N :

46 Unit 6: Bonding Chemical Bonding COVALENT bonds - share equally : NONPOLAR COVALENT - share unequally: POLAR COVALENT - one atom brings both : COORDINATE electrons to share COVALENT

47 Unit 6: Bonding Chemical Bonding IONICCOVALENT - always between- always between a metal and a two nonmetals nonmetalNonpolar - same nonmetal Polar - two different nonmetals **Electronegativity

48 Unit 6: Bonding Chemical Bonding METALLIC -always between two metals -Few valence electrons which float around the nucleus, or nuclei, freely

49 Unit 6: Bonding Homework: pg 79, 1-5; pg 82, and 10-12; pg

50 Unit 6: Bonding Homework: pg 79, 1-5; pg 82, and 10-12; pg ) 2 2) 1 3) 2 4) 1 5) 3

51 Unit 6: Bonding Homework: pg 79, 1-5; pg 82, and 10-12; pg ) 3 7) 4 8)A)B) 9)A)B)

52 Unit 6: Bonding Homework: pg 79, 1-5; pg 82, and 10-12; pg ) 315) 2 11) 216) 2 12) 117) 3 13) 3 14) 1

53 Unit 6: Bonding A molecule can be polar, or called a dipole, if it’s bonds are polar. Although the compound is neutral overall, the electrons are not distributed evenly in its structure  uneven distribution means that each molecule has a positive region on one end and a negative region on the other end

54 Unit 6: Bonding Water, for example, is bent or V- shaped, rather than a linear, sticklike shape as in H-O-H  the oxygen end is an electrically negative region that has a greater concentration of electrons  the hydrogen ends are electrically positive regions that have less concentrations of electrons

55 Unit 6: Bonding The  + and  - indicate partial electrical charges. The partial charges completely cancel, and the molecule is neutral overall

56 Unit 6: Bonding Deciding if a molecule is a dipole is easy, ask yourself these two questions!! 1) Are the bonds polar? If YES, the molecule might be a dipole, keep asking If NO, the molecule is NOT a dipole, you’re done

57 Unit 6: Bonding Deciding if a molecule is a dipole is easy, ask yourself these two questions!! 2) Is the molecule symmetrical? If YES, the molecule is NOT a dipole, all the partial charges will cancel out If NO, the molecule is a dipole, the partial charges are pulling in opposite directions

58 Unit 6: Bonding C O O Linear (AX 2 E 0 ) Dipole moment = 0 NONPOLAR O H H Bent (AX 2 E 2 ) Dipole mom. = 1.84 POLAR

59 B F F Trig. Planar (AX 3 E 0 )  = 0 Unit 6: Bonding F N F F F Trig. Pyramid (AX 3 E 1 )  = All are pulling in opposing directions = Nonpolar All are pulling in same directions = polar

60 Molecule shapes Unit 6: Bonding

61 Unit 6: Bonding Greatest ionic character? Least ionic character? Attraction for electrons?

62 Unit 6: Bonding Greatest ionic character? Greater difference in electronegativity Least ionic character? Smallest difference in electronegativity Attraction for electrons? Electronegative

63 Unit 6: Bonding Distinguishing Bond Types Ionic High melting point Conducts electricity when dissolved in water due to the presence of water, and as a liquid

64 Writing Ionic bonding Unit 6: Bonding

65 Unit 6: Bonding Distinguishing Bond Types Covalent Low melting point Never conducts electricity

66 Unit 6: Bonding Distinguishing Bond Types Metallic High melting point Conducts electricity in the solid state, except mercury, which is a liquid and conducts “sea of mobile electrons”

67 Unit 6: Bonding Homework: pg 86, – 25 pg 88, – 37 pg

68 Unit 6: Bonding Homework: pg 86, – 25 pg 88, – 37 pg

69 Unit 6: Bonding Homework: pg 86, – 25 pg 88, – 37 pg

70 Unit 6: Bonding Homework: pg 86, – 25 pg 88, – 37 pg

71 Unit 6: Bonding Intermolecular Forces:  Forces of attraction between molecules  Several types: Hydrogen bonding Molecule-Ion Van der waals Metallic

72 Unit 6: Bonding Intermolecular Forces: Hydrogen Bonding: the strongest type of force of attraction always exists between the HYDROGEN of one molecule and an OXYGEN, NITROGEN, or FLUORINE of another molecule

73 Unit 6: Bonding Intermolecular Forces: Molecule-Ion: the second strongest type of force of attraction always exists between the WATER molecule and the positive and negative IONS that form when a soluble salt is introduced as a solute

74 Unit 6: Bonding Intermolecular Forces: Van der Waals: the weakest type of force of attraction similar to GRAVITATIONAL attractions, based on size of molecules. Bigger molecules have stronger Van der Waals forces. Explains why all three phases exist in Group 17

75 Unit 6: Bonding Intermolecular Forces: Metallic: unique attraction within metals where the nuclei of metals share all the valence electrons available. Sea of electrons Good conductivity of heat and electricity

76 Unit 6: Bonding Intermolecular Forces: Table H is designed to show trends of intermolecular forces of attraction based on vapor pressure Vapor pressure depicts the number of molecules that have escaped the liquid phase and settled on top of the surface as gas molecules (or vapor)

77 Unit 6: Bonding Intermolecular Forces: Table H is designed to show trends of intermolecular forces of attraction based on vapor pressure Molecules can escape easier if there are WEAK intermolecular forces of attraction between the molecules of liquid

78 Unit 6: Bonding Intermolecular Forces: Table H is designed to show trends of intermolecular forces of attraction based on vapor pressure Propanone has the highest vapor pressure (slope increases the fastest) and therefore the weakest intermolecular forces of attraction

79 Unit 6: Bonding Intermolecular Forces: Table H is designed to show trends of intermolecular forces of attraction based on vapor pressure Ethanoic Acid has the lowest vapor pressure (slope increases the slowest) and therefore the strongest intermolecular forces of attraction

80 Unit 6: Bonding Homework: pg

81 Unit 6: Bonding Homework: pg –