1. Chemical Bonds

2. Atom – the smallest unit of matter “indivisible”
Helium
atom

3. electron shells Atomic number = number of Electrons
Electrons vary in the amount of energy they possess, and they occur at certain energy levels or electron shells.
Electron shells determine how an atom behaves when it encounters other atoms

4. Electrons are placed in shells according to rules:
The 1st shell can hold up to two electrons, and each shell thereafter can hold up to 8 electrons.

5. 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

6. Why are electrons important?
Elements have different electron configurations
different electron configurations mean different levels of bonding

8. Electron Dot Structures
Symbols of atoms with dots to represent the valence-shell electrons
H He:
          
Li Be  B   C   N   O  : F  : Ne :
       
          
Na Mg  Al   Si   P S :Cl  :Ar :
       

9. Chemical bonds: an attempt to fill electron shells
Ionic bonds –
Covalent bonds –
Metallic bonds

10. Learning Check A. X would be the electron dot formula for
A. X would be the electron dot formula for
1) Na 2) K 3) Al
 
B  X  would be the electron dot formula
1) B 2) N 3) P

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

12. 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+

13. Formation of Sodium Ion
Sodium atom Sodium ion
Na  – e  Na +
( = Ne)
11 p p+
11 e e-

14. Formation of Magnesium Ion
Magnesium atom Magnesium ion 
Mg  – 2e  Mg2+
(=Ne)
12 p p+
12 e e-

15. Some Typical Ions with Positive Charges (Cations)
Group 1 Group 2 Group 13
H+ Mg2+ Al3+
Li+ Ca2+
Na+ Sr2+
K+ Ba2+

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

17. 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+

18. Learning Check Give the ionic charge for each of the following:
A. 12 p+ and 10 e-
1) 0 2) 2+ 3) 2-
B. 50p+ and 46 e-
1) 2+ 2) 4+ 3) 4-
C. 15 p+ and 18e-
2) ) 3- 3) 5-

19. Ions from Nonmetal Ions
In ionic compounds, nonmetals in 15 (5A), 16(6A), and 17(7A) gain electrons from metals
Nonmetal add electrons to achieve the octet arrangement
Nonmetal ionic charge:
3-, 2-, or 1-

20. Fluoride Ion     1 - : F  + e : F :     2-7 2-8 (= Ne)
unpaired electron octet
   
: F  e : F :
   
(= Ne)
9 p p+
9 e e-
ionic charge

21. Ionic Bond
Between atoms of metals and nonmetals with very different electronegativity
Bond formed by transfer of electrons
Produce charged ions all states. Conductors and have high melting point.
Examples; NaCl, CaCl2, K2O

23. 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.

25. COVALENT BOND bond formed by the sharing of electrons

26. Covalent Bond
Between nonmetallic elements of similar electronegativity.
Formed by sharing electron pairs
Stable non-ionizing particles, they are not conductors at any state
Examples; O2, CO2, C2H6, H2O, SiC

27. LET’S
FIRST
REVIEW
IONIC
BONDING

28. F K In an IONIC bond, electrons are lost or gained,
resulting in the formation of IONS
in ionic compounds. F K

29. K F

30. K F

31. K F

32. K F

33. K F

34. K F

35. + _ K F

36. K F _ + The compound potassium fluoride
consists of potassium (K+) ions
and fluoride (F-) ions

37. K F _ + The ionic bond is the attraction between the positive K+ ion
and the negative F- ion

38. So
what
are
covalent
bonds?

39. In covalent bonding,
atoms still want to achieve
a noble gas configuration
(the octet rule).

40. But rather than losing or gaining electrons,
In covalent bonding,
atoms still want to achieve
a noble gas configuration
(the octet rule).
But rather than losing or gaining
electrons,
atoms now share an electron pair.

41. The shared electron pair is called a bonding pair
In covalent bonding,
atoms still want to achieve
a noble gas configuration
(the octet rule).
But rather than losing or gaining
electrons,
atoms now share an electron pair.
The shared electron pair
is called a bonding pair

42. Chlorine
forms a
covalent
bond
with
itself
Cl2

43. How
will
two
chlorine
atoms
react? Cl Cl

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

45. 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?

46. Cl Cl

47. Cl Cl

48. Cl Cl

49. Cl Cl

50. Cl Cl
octet

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

52. 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

53. 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

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

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

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

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

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

59. O2
Oxygen is also one of the diatomic molecules

60. O
How will two oxygen atoms bond?

61. O
Each atom has two unpaired electrons

62. O

63. O

64. O

65. O

66. O

67. O

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

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

70. O

71. O O

72. O O

73. O O

74. Both electron pairs are shared.

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

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

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

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

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

81. Covalent Bonds

82. Bonds in all the polyatomic ions and diatomics are all covalent bonds

83. when electrons are shared equally
NONPOLAR COVALENT BONDS
when electrons are shared equally
H2 or Cl2

84. 2. Covalent bonds- Two atoms share one or more pairs of outer-shell electrons.
Oxygen Atom
Oxygen Atom
Oxygen Molecule (O2)

85. when electrons are shared but shared unequally
POLAR COVALENT BONDS
when electrons are shared but shared unequally
H2O

86. Polar Covalent Bonds: Unevenly matched, but willing to share.

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

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

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

90. Metallic Bonds: Mellow dogs with plenty of bones to go around.

91. Ionic Bond, A Sea of Electrons

92. Metals Form Alloys Metals do not combine with metals. They form
Alloys which is a solution of a metal in a metal.
Examples are steel, brass, bronze and pewter.

93. Formula Weights Formula weight is the sum of the atomic masses.
Example- CO2
Mass, C + O + O
43.999

94. Practice
Compute the mass of the following compounds round to nearest tenth & state type of bond:
NaCl;
= 58; Ionic Bond
C2H6;
= 30; Covalent Bond
Na(CO3)2;
23 + 2( x16) = 123; Ionic & Covalent