1. Covalent Bonding

2. Covalent Bonding Covalent Bond:
a bond formed by the sharing of electrons between atoms. (does NOT form charges)
Made up of nonmetals
Molecule: a neutral group of atoms joined together by covalent bonds. (Compounds formed with ionic bonds do NOT have molecules)
Molecular Formula: chemical formula for a molecular compound. It shows how many atoms of each element a molecule contains.

3. Covalent Bonding Examples: ascorbic acid (vitamin C): C6H8O6
trinitrotoluene (TNT): C7H5N3O6
C_____, H_____, N_____, O_____, 6 8 6 7 5 3 6

4. Molecular Nomenclature
Prefix System (binary compounds)
Less electronegative atom comes first.
2. Add prefixes to indicate # of atoms. Omit mono- prefix on first element.
3. Change the ending of the second element to -ide.
most

5. Molecular Nomenclature
PREFIX
mono-
di-
tri-
tetra-
penta-
hexa-
hepta-
octa-
nona-
deca-
NUMBER 1 2 3 4 5 6 7 8 9 10
Only use “mono” on the second element.

6. Naming Covalent Binary Compounds
diphosphorus pentoxide
P2O5 =
CO2 =
carbon dioxide
CO =
carbon monoxide
N2O =
dinitrogen monoxide
phosphorous pentachloride =
PCl5
dinitrogen tetrahydride =
N2H4
dichlorine heptaoxide =
Cl2O7
iodine dioxide =
IO2

7. X O Lewis Structures 2s 2p Electron Dot Diagrams
show valence e- as dots
distribute dots like arrows in an orbital diagram
4 sides = 1 s-orbital, 3 p-orbitals
EX: oxygen X 2s 2p O

8. Ne Lewis Structures Octet Rule
Most atoms form bonds in order to obtain 8 valence e-
Full energy level stability ~ Noble Gases Ne

9. Diatomic Molecules
Diatomic Molecule: a molecule consisting of two atoms.
Diatomic molecules in nature:
H2, N2, O2, F2, Cl2, Br2, I2
“HON and the Halogens”

10. Structural Formula: represents the covalent bonds by dashes and shows the arrangement of covalently bonded atoms
Unshared pair or lone pair: a pair of valence electrons that is not shared between atoms.
Single Covalent Bond: formed by one shared pair of electrons.
Double Covalent Bond: formed by two pairs of shared electrons.
Triple Covalent Bond: formed by three pairs of shared electrons.

13. The halogens form single covalent bonds in their diatomic molecules
The halogens form single covalent bonds in their diatomic molecules. Fluorine is one example.

14. The hydrogen and oxygen atoms attain noble-gas configurations by sharing electrons.

15. The ammonia molecule has one unshared pair of electrons.

16. Methane has no unshared pairs of electrons.

17. Oxygen Molecule Each oxygen atom has two unshared pair of electrons.
This is a double covalent bond.

19. Some covalently bonded substances DO NOT form discrete molecules, they form…
Network Solids: solids in which all of the atoms are covalently bonded.
Diamond, a network of covalently bonded carbon atoms
Graphite, a network of covalently bonded carbon atoms

20. Lewis Structures
Lewis structures are representations of molecules showing all electrons, bonding and nonbonding (lone pairs).

21. Writing Lewis Structures
**These are on your reference sheet**

22. Writing Lewis Structures
Total the number of valence electrons available in the molecule/polyatomic ion (adjust for charge)
If it is an anion, add one electron for each negative charge.
If it is a cation, subtract one electron for each positive charge.
PCl3
(7) = 26

23. Writing Lewis Structures
Write the symbols for the given formula with some space between them. Put the one with the lowest electronegativity in the center and the others on each of the four sides.
Exception: Hydrogen can NEVER be in the center.
If there is a Carbon atom, it is the center atom.
Draw one dash between the symbols to represent a bond…

24. Writing Lewis Structures
… Fill the octets of all the outer atoms with lone pairs.

25. Writing Lewis Structures
Check for full octets & total number of electrons used.
…If too many e-s used, erase lone pairs and make multiple bonds.
…If too few e-s used, expand central atom octet.
…odd number of valence e-s = octet deficient

26. Writing Lewis Structures

27. Writing Lewis Structures
If the molecule is a polyatomic ion, put brackets around the structure and write the charge in the upper right corner.

28. Examples
Cl2 O2 N2

29. Cl Cl O O N N #s of Covalent Bonds Single Bond: 2 e- shared
Double Bond: 4 e- shared
Triple Bond: 6 e- shared

30. Examples
NH3
CCl4
H2S
SO3

31. Examples
ClO4-

32. Polyatomic Ions and covalent bonding “CHLORATE”-1 O
Cl O
Chlorine has 7 valence e-
Each oxygen has 6 valence e-
When ClO3 comes together they form 3 single covalent bonds
One additional electron completes chlorine with a full valence shell, making this a covalently bonded group with an ionic charge of -1

33. Examples
CO32-

34. Polyatomic Ions and covalent bonding “CARBONATE”-2
Carbon has 4 valence e- O
C O
Each oxygen has 6 valence e-
When CO3 comes together they form 2 single covalent bonds and 1 double covalent bond
Two additional electrons completes carbon with a full valence shell, making this a covalently bonded group with an ionic charge of -2

35. Examples
PO43-

36. Polyatomic Ions and covalent bonding “PHOSPHATE”-3 O
O P O
Phosphorus has 5 valence e-
Each oxygen has 6 valence e-
When PO4 comes together they form 3 single covalent bonds
Three additional electrons completes phosphorus with a full valence shell, making this a covalently bonded group with an ionic charge of -3

38. VSEPR Theory
Most graphics from:

39. VSEPR Theory
VSEPR Theory (Valence-shell electron-pair repulsion theory): the repulsion between electron pairs causes molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible.

43. 2 Charge Clouds
AX2 CO2

44. 3 Charge Clouds
AX3 CH2O
Bent or
AX2E SO2

46. 4 Charge Clouds
AX4 CH4
AX3E NH3
Bent or
AX2E2 H2O

48. Quiz
What is the geometry around the central atom in each of the following molecular models?
How many lone pairs (not shown) are around each central atom?

49. Above is a ball-and-stick molecular model representation of acetaminophen, the active ingredient in such over-the-counter headache remedies as Tylenol (red = O, gray = C, blue = N, ivory = H):
What is the molecular formula of acetaminophen?
What is the geometry (angles) around each carbon and nitrogen? (The lines between atoms indicate connections only, not whether the bonds are single, double, or triple.)
Indicate the positions of multiple bonds (double & triple) in acetaminophen.

51. C8H9NO2
120
120 LP
120 LP
107 LP
104.5
120
120
109.5
120 LP LP

52. Polarity

53. Bond Polarity
Most bonds are a blend of ionic and covalent characteristics.
Difference in electronegativity determines bond type.
E difference: >1.7
E difference:
E difference:

54. Bond Polarity Electronegativity
Attraction an atom has for a shared pair of electrons.
higher e-neg atom δ-
lower e-neg atom δ+

55. Bond Polarity
Electronegativity Trend
Increases up and to the right.

56. Table of Electronegativity

57. Bond Polarity Nonpolar Covalent Bond e- are shared equally
symmetrical e- density
usually identical atoms

58. δ+ δ- Bond Polarity Polar Covalent Bond e- are shared unequally
asymmetrical e- density
results in partial charges (dipole) δ+ δ-

59. Bond Polarity
Ionic Bond
e- are transferred

60. Bond Polarity Nonpolar Polar Ionic e- shared equally
e- shared unequally
Ionic
e- transferred
E difference:
E difference:
E difference: >1.7

61. Bond Polarity Examples: Cl2 HCl 3.0-3.0=0.0 Nonpolar 3.0-2.1=0.9 NaCl
=2.1
Ionic

62. Bond Polarity - + Nonpolar Covalent – equally shared e-
Polar Covalent - partial charges, e- shared unequally + -

63. Polar Molecule
One end of the molecule is slightly negative and the other end is slightly positive
Caused by the presence of a polar bond in the molecule. (the structure is not symmetrical)
A molecule that has two poles is called a dipolar molecule, or dipole.

64. How to Determine Molecular Polarity
Are There Polar Bonds?
Non-Polar
Molecule NO
Check the
Molecule Shape
YES
Non-Polar
Molecule
YES
Are the polar bonds
symmetrical around
the molecule?
Polar
Molecule NO

65. The water dipole

66. The ammonia dipole

67. Self Test Is CO2 a covalent or ionic compound? What is CO2 ’s name?
What is the electronegativity difference between C and O?
Does CO2 have polar bonds?
Is CO2 a polar molecule overall?
. . O C :

68. CHEMICAL FORMULA/Smallest unit
IONIC
COVALENT
Formula
Unit
NaCl
Molecular
Formula
CO2

69. NaCl NaNO3 COMPOUND more than 2 elements 2 elements Binary Compound
Ternary
Compound
NaNO3

70. ION (charged particle)
1 atom
2 or more atoms
Monatomic
Ion
Na+
Polyatomic
Ion
NO3-

71. Bonding Summary Ionic Covalent Transfer of electrons
Octet achieved by:
Transfer of electrons
(forming + & - ions)
Sharing electrons
Made of:
Metal cation (+) & Nonmetal anion (-)
Nonmetals (above metalloid line) (no charges)
Characteristics:
Brittle
Small and very large molecules
Structure:
Arranged in alternating
+ & - ions (crystal lattice)
Individual molecules
Representative Particle:
Formula Unit:
(lowest whole number ratio of atoms)
Molecule:
(group of joined atoms)

72. Yes, when dissolved in water or melted
Bonding Summary
Ionic
Covalent
Physical State:
Solid
Solid, Liquid, Gas
Melting Point:
High
Low
Electrical Conductivity:
Yes, when dissolved in water or melted No

73. Bonding Summary Metallic Metallic
Octet achieved by:
Valence e- delocalized around metal atoms
Made of:
Metal cation (+) & Valence electrons
Characteristics:
Maleable, ductile, lustrous
Structure:
“Electron Sea”
Representative Particle:
Atom
Metallic
Physical State:
Solid (except Hg)
Melting Point:
High
Electrical Conductivity:
Yes (any form)

74. Ionic Bonding - Crystal Lattice
Types of Bonds
Ionic Bonding - Crystal Lattice

75. Covalent Bonding - True Molecules
Types of Bonds
Covalent Bonding - True Molecules
Diatomic Molecule

76. Metallic Bonding - “Electron Sea”
Types of Bonds
Metallic Bonding - “Electron Sea”

78. Quiz - answer the following on a sheet of paper
The following ball-and-stick molecular model is a representation of thalidomide, a drug that causes birth defects when taken by expectant mothers but is valuable for its use against leprosy. The lines indicate only the connections between atoms, not whether the bonds are single, double, or triple (red = O, gray = C, blue = N, ivory = H):
(a) What is the molecular formula of thalidomide?
(b) Indicate the positions of the multiple bonds in thalidomide.
(c) What is the geometry around each carbon and each nitrogen?