1. Chapter 8
Covalent Bonding I

2. Molecules and Molecular Cpds
noble gases (e.g. He and Ne) and most elements are monatomic.

3. Molecules and Molecular Cpds
Covalent cpds
atoms held together by sharing e- are joined by a covalent bond to form covalent cpds
Non-metals
e.g. [O2 ;not a cpd], CO2, C6H12O6
element

4. Molecules and Molecular Cpds
Covalent bonds
not so strong as Ionic bonds (electrostatic attractions).
Covalent cpds: made up of ALL nonmetals (how about ionic cpds?)

5. Molecules and Molecular Cpds
a neutral group of atoms (all nonmetals) joined together by covalent bonds.
may be a cpd (e.g. CO2) or an element (e.g. N2)
covalent cpds = molecular cpds

6. Molecules and Molecular Cpds
e.g. air contains oxygen molecules (O2) and nitrogen molecules (N2)---not cpds
A diatomic element consists of 2 atoms.
e.g. 7 diatomic elements are H2, N2, O2, F2, Cl2, Br2, I2

7. Diatomic Molecules Hydrogen Colorless gas H2 Nitrogen N2 Oxygen
Pale blue gas O2
Fluorine
Pale yellow gas F2
Chlorine
Pale green gas
Cl2
Bromine
Reddish brown liquid
Br2
Iodine
Lustrous, dark purple solid I2

8. A Hydrogen Molecule 2 H atoms share a pair of e- in a covalent bond.
A covalent bond is formed by 2 shared e-.

9. Covalent Bonds
2 of the same atoms form a covalent bond, e.g., when 2 F atoms form the F2 molecule.
a pair of valence e- are shared---single covalent bond (2 shared e-).
Form octets of for both atoms
Shared pair of e-

10. Molecules and Molecular Cpds
Molecular cpd (covalent cpd):
- cpds composed of molecules
e.g. H2O , CO2 , C6H12O6

11. Molecules and Molecular Cpds

12. Physical Properties Properties Ionic cpd Covalent cpd Example NaCl
State at room temperature
Crystalline solid
Solid, liquid or gas
Melting point
High
Low
Conduct electricity in liquid state
Yes No
Water solubility
Conduct electricity in aqueous solution
poor

13. Molecular Formulas

14. Covalent Bonds
All diatomic elements (F2, Cl2, Br2, I2, O2, N2, and H2) have covalent bonds.
are molecules (not molecular cpds)
The other molecules are ALL cpds
Most of the elemental diatomic molecules are gases at room temp—Cl2, F2, O2, N2, and H2.

15. Modeling Water
2 covalent bonds.
octet
duplet

16. Lone (unshared) pair
3 covalent bonds
Bonding (shared) pair

17. A Model for Ammonia Each H shares a pair of e- with the N.
Lone pair
Each H shares a pair of e- with the N.
N’s remaining 2 e- form a lone pair.
N has a complete octet of e-.

18. Modeling Carbon Dioxide
double bond
sharing 2 pairs of e- between 2 atoms.

19. Double Bonds and Triple bonds
F−F
O=O
N≡N
O=C=O

20. Naming Binary Molecular Cpds
9.3
(1) Name the elements in the order listed in the formula.
(2) Use prefixes to indicate the # of each kind of atom.

21. Naming Binary Molecular Cpds
9.3
(3) Omit the prefix mono- when the formula contains only 1 atom of the 1st element in the name. e.g. CO2 (we don’t say monocarbon)
(4) The suffix of the name of the 2nd element is -ide.

22. Writing Formulas for Binary Mol. Cpds
9.3
(5) Use the prefixes in the name to tell the subscript of each element in the formula.
(6) Then write the correct symbols for the 2 elements with the appropriate subscripts.

23. Naming Binary Molecular Cpds
9.3

24. Naming Binary Molecular Cpds
NF3
SF4
CO2
SbCl3 CO
NH3
H2O
CF4
CS2
P4S3
BCl3
SO2
IF7
SO3
PCl5
CCl4
C2O5
MgCl2
HCl
SiCl4

25. CST problem 1
(picture of a circuit) The above picture shows a light bulb connected to a battery with the circuit interrupted by a solution. When dissolved in the water to form a 1.0 molar solution, all of the following substances will complete a circuit allowing the bulb to light except
A hydrochloric acid
B sodium nitrate
C sucrose
D ammonium sulfate

26. Table of common molecules
CST problem 2
Table of common molecules
Name
Hydrogen
Chlorine
Ammonia
Methane
Molecular Formula H2
Cl2
NH3
CH4
What type of bond do all of the molecules in the table above have in common?
A covalent
B ionic
C metallic
D polar

27. The End