1. Covalent Compounds Contain 2 or more nonmetals.
Made of molecules—NOT IONS.
2 nonmetals can combine in more than 1 way!
CO2 is a gas that we breathe out.
CO is a colorless, odorless, & deadly gas
Both are carbon oxides, but it is important to distinguish between them.

2. Naming Covalent
The number of each element (subscript) is written as a prefix in the both parts of the name.
Change the ending to –ide on the 2nd element
Examples:
CO2 is carbon dioxide
CO is carbon monoxide
1-mono
2-di
3-tri
4-tetra
5-penta
6-hexa
7-hepta
8-octa
9-nona
10-deca
IMPORTANT: The mono prefix is omitted only on the first element.
*On the back of your P.T.

3. Formulas of Covalent
The prefixes on each element tell you the subscripts in the formula
Example: tetraiodine nonoxide
I4O9

4. Lets try some examples
Given the formula, name the following molecular compounds.
N2O
Dinitrogen monoxide
PCl3
Phosphorus trichloride
SF6
Sulfur hexafluoride
CS2
Carbon disulfide

5. More examples
Given the name, what’s the formula for the following compounds.
Nitrogen trifluoride
NF3
Disulfur dichloride
S2Cl2
Dinitrogen tetroxide
N2O4
Phosphorus pentafluoride
PF5

6. Properties of Covalent Compounds
Chapter 8

7. Molecular Compounds Molecular = Covalent
In a covalent bond, electrons are shared
Diatomic molecule—a molecule consisting of 2 atoms
Hydrogen = H2
N2 O2 F2 Cl2 Br2 I2

8. Properties Have lower melting/boiling points than ionic
Most are gases or liquids at room temp.
Composed of 2 (or more) nonmetals
When writing a molecular formula, the subscripts are not always in the lowest ratio.
Ex. H2O2

9. Covalent Bonding Molecules can form single, double, and triple bonds
Single: share 1 pair of e- (2 e-)
Shown as a single line
Double: share 2 pairs of e- (4 e-)
Shown as a double line
Triple: share 3 pairs of e- (6 e-)
Shown as a triple line
Acetone

10. Bond Strength
Many covalent compounds are more stable than the atoms alone.
Bond Dissociation Energy—the energy required to break the bond between 2 covalently bonded atoms
A large dissociation energy corresponds to a strong covalent bond

11. Bonding Theories VSEPR Theory: Valence Shell Electron Pair Repulsion
The repulsion between e- pairs causes the shape of molecules to adjust so e- pairs are as far apart as possible

12. Molecular Shapes Linear Trigonal Planar Bent Pyramidal Tetrahedral
Trigonal Bipyramidal
Octahedral
Square Planar
T-Shaped

13. Polarity and Molecules
Covalent Bonds can be polar or nonpolar
Nonpolar—formed when e- are shared equally between 2 atoms
Bonds can be nonpolar in 2 ways
Nonpolar covalent bonds
Ex. Diatomic elements: H2 N2 O2 F2
Polar Bonds due to symmetry
CH4

14. Polar Bonds Formed when e- are shared unequally between 2 atoms
The more electronegative atom attracts e- more strongly and gains a slightly negative charge
The less electronegative atom has a slightly positive charge
Electronegativity Differences & Bond Types
Electronegativity Difference Range
Bond Type
Nonpolar Covalent
Slightly Polar Covalent
Very Polar Covalent
≥2.0
Ionic

15. Characteristics of Ionic & Covalent
Representative unit
Formula Unit
Molecule
Bond formation
e- transfer
(gained or lost)
e- shared
Type of elements
Metal + Nonmetal
(& polyatomic ions)
Nonmetal + Nonmetal
Physical state
Solids
Solid, liquid, gas
Melting Point
High
Low
Solubility in water
High to Low
Electrical conductivity in aqueous solution
Good conductor
Poor to nonconducting