(p. 232)

6.2 Molecular Compounds

2 types of compounds

1. Ionic compound:

a compound made of oppositely charged ions

2. Molecular compound:

a compound formed when atoms of two or more different

elements share electrons

Molecular compounds

When atoms share a pair of electrons to form full outer

energy levels

form a covalent bond

form a molecular compound

Copyright © 2010 McGraw-Hill Ryerson Ltd.

Reviewing Molecular BondsClick the “Start” button to review the formation of covalent

bonds and molecular compounds.

Molecular compounds

Composed of 2 or more non-metals

Smallest discrete particle of a pure substance, which has one

ore more shared pairs of electrons a molecule

Also called covalent compounds

3D Water Molecule Model Bohr-Rutherford Water Molecule

Diatomic molecule

Composed of 2 atoms of the same element

Covalently bonded

7 diatomic molecules:

1. Nitrogen gas N2

2. Oxygen gas O2

3. Fluorine gas F2

4. Chlorine gas Cl25. Bromine Br2

6. Iodine I2

7. Hydrogen gas H2

3D Oxygen Molecule Model

Properties of Molecular Compound Covalent bonds are very strong BUT attraction between

molecules is weak

leads to the following properties:

Made up of non-metals elements

Poor conductors of heat and electricity

Low melting points

Low boiling points

Soft

Not very soluble in water

Used to

insulate wire

CO2 is dissolved under

pressure in soft drinks

Attraction between

molecules is weak

Plastics Made of giant molecular compounds called polymers

Many ethylenemolecules joined together to make this class

of plastics called polyethylenes

Number of ethylene molecules and their density determines

the type of plastics:

Shopping bags

Toys

Bottles/containers

CON:

Do not degrade easily

Chemicals can leach out in landfills

Discarded plastics hazardous to wildlife

Compounds

Ionic compounds Molecular compounds

metal + non-metal non-metal + non-metal

transfer of electrons sharing of electrons

form ions (+ and - ) do not form ions

ionic bonds covalent bonds

ionic compound molecular compound /

covalent compound

Copyright © 2010 McGraw-Hill Ryerson Ltd.

Section 6.2 Review

Concepts to be reviewed:

• What is a molecular compound? What types of elements usually

form molecular compounds?

• What are the characteristic properties of molecular compounds?

Why do they display these properties?

• What are the advantages and disadvantages of producing and

using plastics?

How to Name Molecular Compounds1. Name the first element

2. Name the second element using the suffix –ide

3. Use prefix to represent the number of atoms of each element

4. Check for exceptions:1. The prefix mono- is not used for the first element

2. When mono- is followed by oxide, use only one “o” monoxide

Memorize

this table!

C COO O

Formula Chemical Name

S2F6

N2O5

NO

P3Cl7

disulfur hexafluoride

dinitrogen pentaoxide

nitrogen monoxide

triphosphorus heptachloride

PRACTICE:

How to Write Chemical Formula for

Molecular Compounds

1. Write symbol for 1st element

2. Write symbol for 2nd element

3. Determine number of atoms for each element from the

prefixes

PRACTICE

Chemical Name Chemical Formula

dinitrogen tetraoxide

carbon disulfide

dihydrogen monoxide

N2O4

CS2

H2O