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

2. Valence Electrons
Valence electrons are the electrons in the highest occupied energy level of the atom.
Valence electrons are the only electrons generally involved in bond formation.

3. Electron Configuration of Sodium
1s2 2s2 2p6 3s1
Which is the valence electron for Na?
Answer: 1s2 2s2 2p6 3s1

4. Na , 11 e

5. Na + , 10e

6. 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

7. 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.

8. 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

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

12. 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 :
       

13. Electron Dot Structure or Lewis Dot Diagram
A notation showing the valence electrons surrounding the atomic symbol.

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

15. 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

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

17. 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+

18. Check your Neighbor
When Na, (Z= 11) loses its valence electron, what element does its configuration look like ?
Neon
Potassium
Beryllium
Sodium
C. discover the property called inertia.

19. A Stable Octet
When the valence shell is full, the atom is stable, less likely to react.
Example: Noble (Inert Gases) Kr

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

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

22. Equations for the Formation of Cations
H  H e-
Li  Li e-
Mg:  Mg e-

23. Equations for the Formation of Anions
: F : + e-  : F - :

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

25. 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+

26. 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+

27. 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-

28. Ionic Compounds Are made up of: a metal and a nonmetal ion.
polyatomic ions.

29. Ions from Nonmetal Ions
In ionic compounds, nonmetals in 15, 16, and 17 gain electrons from metals
Nonmetal add electrons to achieve the octet arrangement
Nonmetal ionic charge:
3-, 2-, or 1-

30. 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

31. 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

33. Ionic Bonds: One Big Greedy Thief Dog!

34. 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.

36. Example: Which of the following compounds are ionic? NaCl CO2 CO KF
KNO3

37. Some Common Ions

38. COVALENT BOND bond formed by the sharing of electrons

39. 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

40. Covalent Bonds

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

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

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

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

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

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

47. POLAR COVALENT BOND
the electrons shared by the atoms spend a greater amount of time closer to one particular atom
This creates a partial negative end and a partial positive end

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

49. 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

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

51. Ionic Bond, A Sea of Electrons

52. 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.

53. Chemical Formula
A representation of the kinds and number of atoms in a substance.

54. Formula Unit
A chemical formula that shows the lowest whole number ratio of the atoms (ions) in an ionic compound.
Example: KCl, Mg Cl2

55. The formula unit is used because ionic compounds have a lattice arrangement of ions. Ex: NaCl
Which ball represents the Na?

56. NUMBER OF BONDS BETWEEN ATOMS
Single bonds – one pair of electrons; longest bond length; weakest bond
Cl – Be – Cl
Double bonds – two pairs of electrons
O=C=O
Triple bonds – three pairs of electrons; shortest bond length; strongest bond
N N

57. INTERMOLECULAR FORCES
London Dispersion Forces (Van der Waals Forces)
1. weakest of all intermolecular forces
2. the attractive or repulsive force between molecules (or between parts of the same molecule)
Dipole-Dipole Interactions
1. between polar molecules
Hydrogen Bonds
1. strongest of all intermolecular forces
2. hydrogen bonded to a very electronegative atom (O,N,F)
H F
N N

58. Electronegativity & Bond Type
Example
Nonpolar covalent
H-H (0.0)
Polar covalent
H-Cl (0.9)
>1.7
Ionic
Na-Cl (2.1)

59. VSEPR Valence Shell Electron-Pair Repulsion
A. predicts the shape of individual molecules based upon the extent of electron-pair electrostatic repulsion
B. Double bonds count as one pair of electrons

60. Linear 180° 3 2 BeCl2 CO2 Bent 104.5 4 H2O Trigonal Pyrimidal 107° 1
Bond Angle
# atoms
# e- pairs
# unshared e- pairs
Example
Linear
180° 3 2
BeCl2
CO2
Bent
104.5 4
H2O
Trigonal Pyrimidal
107° 1
NH3
Tetrahedral
109.5 5
CH4
Trigonal Planar
120°
BF3

61. SO2
Bent 104.5°

62. CO2
Linear 180°

63. CF2Cl2
Tetrahedral 109.5°

64. NH4+
Tetrahedral 109.5°

65. O3
Bent 104.5°

66. BeCl2
Linear 180°

67. H2O
Bent 104.5°

68. SO42-
Tetrahedral 109.5°

69. NH3
Trigonal Pyrimidal 107°

70. CH4
Tetrahedral 109.5°

71. BCl3
Trigonal Planar 120°