1. Covalent Bonds
2a. Students know atoms combine to form molecules by sharing electrons to form covalent or metallic bonds or by exchanging electrons to form ionic bonds.
2b. Students know chemical bonds between atoms in molecules such as H2, CH4, NH3, H2CCH2, N2, Cl2, and many large biological molecules are covalent.

2. Chemical Bonds
Bonds – forces that hold groups of atoms together and make them function as a unit.
3 Types:
Ionic Bonds
Covalent Bonds
Metallic Bonds

3. Happy Atoms have a full Octet!
Covalent Bonds
Bonds between nonmetals and nonmetals!
Sharing of Electrons!
Resulting particle is called a molecule!
Want 8 electrons to look like a noble gas (octet rule)
Happy Atoms have a full Octet!

4. Co = with or together Valent = to be strong
Two electrons shared together have the strength to hold two atoms together in a bond.

5. Molecules Many elements found in nature are in the form of molecules:
a neutral group of atoms joined together by covalent bonds.
i.e. air contains oxygen molecules, consisting of two oxygen atoms joined covalently
Called a “diatomic molecule” (O2)

6. Diatomic Molecules – molecule consisting of 2 atoms covalently bonded together
7 diatomic molecules: Iodine, Hydrogen, Nitrogen, Bromine, Oxygen, Chlorine, and Fluorine

7. Can form single, double, or triple covalent bonds.
Single bond – one pair of shared electrons
Double bond – two pairs of shared electrons
Triple bond – three pairs of shared electrons
I have no bright or clever friends!

8. Four main types of macromolecules in the human body
Forms large macromolecules (a big long chain of molecules – like in the human body)!
Four main types of macromolecules in the human body
Carbohydrates
Proteins
Lipids (Fats)
Nucleic Acids
Monomers and Polymers

9. How does H2 form?
(diatomic hydrogen molecule)
The nuclei repel each other, since they both have a positive charge (like charges repel). + + + +

10. But, the nuclei are attracted to the electrons
They share the electrons, and this is called a “covalent bond”, and involves only NONMETALS! + +

11. Covalent Bonds Nonmetals hold on to their valence electrons.
They can’t give away electrons to bond.
But still want noble gas configuration.
Get it by sharing valence electrons with each other = covalent bonding
By sharing, both atoms get to count the electrons toward a noble gas configuration.

12. Covalent bonding Example
Fluorine has seven valence electrons (but would like to have 8) F

13. Covalent bonding Example
Fluorine has seven valence electrons
A second atom of fluorine also has seven F F

14. Covalent bonding Example
Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons… F F

15. Covalent bonding Example
Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons… F F

16. Covalent bonding Example
Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons… F F

17. Covalent bonding Example
Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons… F F

18. Covalent bonding Example
Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons… F F

19. Covalent bonding Example
Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons…
…both end up with full orbitals F F

20. Covalent bonding Example
Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons…
…both end with full orbitals F F
8 Valence electrons

21. Covalent bonding Example
Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons…
…both end with full orbitals F F
8 Valence electrons

22. Chlorine
forms a
covalent
bond
with
itself
Cl2

23. How
will
two
chlorine
atoms
react? Cl Cl

24. Cl Cl Each chlorine atom wants to
gain one electron to achieve an octet

25. Cl Cl do to achieve an octet? What’s the solution – what can they
Neither atom will give up an electron –
chlorine is highly electronegative.
What’s the solution – what can they
do to achieve an octet?

26. Cl Cl

27. Cl Cl

28. Cl Cl

29. Cl Cl

30. Cl Cl
octet

31. Cl Cl octet circle the electrons for each atom that completes
their octets

32. Cl Cl The octet is achieved by each atom sharing the
electron pair in the middle
circle the electrons for
each atom that completes
their octets

33. Cl Cl The octet is achieved by each atom sharing the
electron pair in the middle
circle the electrons for
each atom that completes
their octets

34. Cl Cl This is the bonding pair circle the electrons for
each atom that completes
their octets

35. Cl Cl It is a single bonding pair circle the electrons for
each atom that completes
their octets

36. Cl Cl It is called a SINGLE BOND circle the electrons for
each atom that completes
their octets

37. Single bonds are abbreviatedCl Cl
Single bonds are abbreviated
with a dash
circle the electrons for
each atom that completes
their octets

38. This is the chlorine molecule,Cl Cl
This is the chlorine molecule,
Cl2
circle the electrons for
each atom that completes
their octets

39. O2
Oxygen is also one of the diatomic molecules

40. O
How will two oxygen atoms bond?

41. O
Each atom has two unpaired electrons

42. O

43. O

44. O

45. O

46. O

47. O

48. O Oxygen atoms are highly electronegative.
So both atoms want to gain two electrons.

49. O Oxygen atoms are highly electronegative.
So both atoms want to gain two electrons.

50. O

51. O O

52. O O

53. O O

54. Both electron pairs are shared.

55. O O
6 valence electrons
plus 2 shared electrons
= full octet

56. O O
6 valence electrons
plus 2 shared electrons
= full octet

57. O O
two bonding pairs,
making a double bond

58. O O =
For convenience, the double bond
can be shown as two dashes.

59. This is the oxygen molecule,=
this is so cool!!
This is the oxygen molecule, O2

60. Dot diagram for Carbon dioxide
CO2 - Carbon is central atom ( more metallic )
Carbon has 4 valence electrons
Wants 4 more
Oxygen has 6 valence electrons
Wants 2 more C O

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

62. Carbon dioxide
Attaching the second oxygen leaves both of the oxygen 1 short, and the carbon 2 short O C O

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

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

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

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

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

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

69. O C O Carbon dioxide The only solution is to share more
Requires two double bonds
Each atom can count all the electrons in the bond O C O

70. O C O Carbon dioxide The only solution is to share more
Requires two double bonds
Each atom can count all the electrons in the bond
8 valence electrons O C O

71. O C O Carbon dioxide The only solution is to share more
Requires two double bonds
Each atom can count all the electrons in the bond
8 valence electrons O C O

72. O C O Carbon dioxide The only solution is to share more
Requires two double bonds
Each atom can count all the electrons in the bond
8 valence electrons O C O

73. How to draw them? Use the following guidelines:
Add up all the valence electrons.
Count up the total number of electrons to make all atoms happy.
Subtract; then Divide by 2
Tells you how many bonds to draw
Fill in the rest of the valence electrons to fill atoms up.

74. N H Example NH3, which is ammonia
N – central atom; has 5 valence electrons, wants 8
H - has 1 (x3) valence electrons, wants 2 (x3)
NH3 has 5+3 = 8
NH3 wants 8+6 = 14
(14-8)/2= 3 bonds
4 atoms with 3 bonds N H

75. H H N H Examples Draw in the bonds; start with singles
All 8 electrons are accounted for
Everything is full – done with this one. H H N H

76. Example: HCN HCN: C is central atom
N - has 5 valence electrons, wants 8
C - has 4 valence electrons, wants 8
H - has 1 valence electron, wants 2
HCN has = 10
HCN wants = 18
(18-10)/2= 4 bonds
3 atoms with 4 bonds – this will require multiple bonds - not to H however

77. H C N HCN Put single bond between each atom Need to add 2 more bonds
Must go between C and N (Hydrogen is full) H C N

78. H C N HCN Put in single bonds Needs 2 more bonds
Must go between C and N, not the H
Uses 8 electrons – need 2 more to equal the 10 it has H C N

79. H C N HCN Put in single bonds Need 2 more bonds
Must go between C and N
Uses 8 electrons - 2 more to add
Must go on the N to fill its octet H C N

80. Another way of indicating bonds
Often use a line to indicate a bond
Called a structural formula
Each line is 2 valence electrons H O H H O H =

81. NonMetals and NonMetals
Covalent Bonds
NonMetals and NonMetals
Share Electrons
Large Molecules