Chapter 2:
CHEMICAL
COMPOUNDS AND
BONDING
§2.2 - MOLECULAR
ELEMENTS AND
COMPOUNDS
Grade 11 University
Chemistry
Cardinal Ambrozic
C.S.S.
MOLECULAR ELEMENTS
Pure substance consisting of molecules
containing one type of atom
 Diatomic Elements – Stable elements made up
of two atoms
 I Never Have Clean Briefs On Fridays
(Example I = Iodine, I2)
 Ozone, O3 is another example of a molecular
element (that is not diatomic – its triatomic)
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MOLECULAR COMPOUNDS
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Carvone
Consist of at least two different non-metal
elements
Some molecular compounds contain metals and
metalloids
Two molecular compounds may have the same
structure, but because of slight variations, can
exhibit different physical properties.
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Properties of Molecular
Compounds
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Covalent Bonding
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Solids, liquids and gases at room temperature
Varying textures (soft, waxy, flexible, crystlline)
Have low melting points and boiling points
Poor conductor of electricity
Generally have low solubility in water
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Covalent bonds are bonds that result from the
sharing of valence electrons by two atoms.
The unpaired electron from each atom is called a
bonding electron
We get bonding capacity from the number of
boding electrons an atom has available
Group
1
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15
16
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# of valence
electrons
1
4
5
6
7
Bonding
Capacity
1
4
3
2
1
6
1
Forming the Covalent Bond…
Forming the Covalent Bond
H
1P
0N
Multiple Covalent Bonds
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Multiple Covalent Bonds
Double Bonds
- Can exist between the
same elements or
different elements
In covalent bonding, atoms can share two or
three pairs of electrons
Example: O2, each oxygen has six electrons in
its valence shell – each atom requires two
electrons to achieve a stable octet. Oxygen
shares two pairs of electrons – this is a double
bond.
Triple Bonds
- When atoms share
three pairs of
electrons
Exceptions to the Octet Rule
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H
1P
0N
Lewis Structures

The Octet Rule is not always perfect
Regardless, NO2 always has one extra electron
(this property makes the gas toxic)
Some elements do not require eight electrons to
be stable. For example, sulfur can achieve
stability with twelve electrons

A system originated by Lewis for showing covalent
bonding
The shared pair of electrons are replaced with a line
1 shared pair = single bond
2 shared pairs = double bond
 3 shared pairs = triple bond
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The unshared electrons are shown as dots
Unshared pairs of electrons are called lone pairs.
Shared pairs of electrons are called bonding pairs.
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Lewis Structures vs.
Structural Formulas
Drawing Lewis Structures
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Lewis Structures show the bond
between the atoms and the lone
pairs of electrons around each
atom
Instructions for Drawing Lewis Structures are
on Page 64-65
Homework:
- Page 65 #1 a-j (Note: d is CO2)
- Page 69 #1(a, even letters), 2-7
Structural formulas show the
bonds between the atoms, but not
the lone pairs
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