Review
 Write the electron configuration for an atom of carbon
and chlorine.
 Determine the empirical and molecular formula for a
compound consisting of 7.8% carbon and 92.2%
chlorine. The molecular mass of the compound is 154
g/mole.
 Write the name for the compound.
What is a covalent bond?
 A covalent bond forms between two atoms that are
sharing one or more pair of electrons.
 Usually occurs when the electronegativity difference
between the two elements is small (<1.7)
 Covalent bonds form between two nonmetals.
 The bond results from an overlapping of orbitals.
 A covalent bond is a weaker bond than an ionic bond.
 Properties of compounds resulting from a covalent
bond include: low melting point, gases or liquids at
room temp (some are soft solids), do not conduct
electricity, many are insoluble in water.
Naming covalently bonded
compounds.
 The first element is named according to the element
name.
 An –ide ending is added to the name of the second
element.
 Numerical prefixes are used to indicate the number of
each type of atom present.
Numerical Prefixes
Prefix
Number
*Mono (only used with the second
element)
1
Di
2
Tri
3
Tetra
4
Pent
5
Hex
6
Hept
7
Oct
8
Non
9
Dec
10
Name the following compounds











CO2
CO
N2O
NO
NO2
N2O3
N2O4
N2O5
PCl5
PCl3
SF6
Write the formulas for the
following compounds:
 Sulfur trioxide
 Dioxygen difluoride
 Tetraphosphorus decaoxide
 Diboron trioxide
 Arsenic pentafluoride
 Silicon dioxide
 Monohydrogen dioxide
 Nitrogen trihydride
Types of Covalent Bonds
 A single covalent bond occurs when one pair of
electrons (2 electrons) are shared between two atoms.
 A double covalent bond occurs when two atoms share
two pairs (4 electrons) of electrons.
 A triple covalent bond occurs when two atoms share
three pairs (6 electrons) of electrons.
Drawing Lewis Dot Structures
 Lewis dot structures can be drawn to represent the bonding
that occurs within a covalent molecule.
 Atoms of hydrogen and halogens can only form one single
bond each. (They only need to share 1 electron to form a
complete octet).
 Lines represent the shared pairs of electrons or the
chemical bonds between atoms. Unshared pairs are
represented by dots or a line.
Example
 Draw the Lewis Dot Structure for CCl4
Example #2
 Draw the Lewis dot structure for a molecule of NH3.
Example #3
 Draw the Lewis dot structure for H2O.
For molecules involving atoms other
than halogens or hydrogen
 Use the formula “N-A = S” to determine the number and




type of bonds within the molecule.
N represents the total number of valence electrons needed
by all atoms to have a complete octet.
A represents the total number of valence electrons
available in all atoms within the molecule.
S represents the total number of electrons that will need to
be shared in order to form complete octets for each atom.
Divide the number shared by 2 to determine the number of
bonds that will form.
Draw the Lewis dot structure
for O2.
 N= 16
 A=12
 S=4
 4/2=2
 Therefore, 2 bonds are needed (or 4 electrons need to
be shared) in order for this molecule to form.
Draw the Lewis dot structure
for N2.
 Step 1: Solve the equation “N-A = S”
 Step 2: Divide “S” by 2.
 Step 3: Draw the general structure of the molecule
 Step 4: Fill in the bonds.
 Step 5: Fill in the remaining valence electrons so that
all atoms have a stable arrangement (8 electrons)
Draw the Lewis dot structure for CO2
 Step 1: 24 – 16 = 8
 Step 2: 8/2= 4
 Step 3:
Draw the Lewis dot structure for HCN
 Step 1: 18-10 = 8
 Step 2: 8/4 = 2
 Step 3:
Homework:
 Name and Draw Lewis Dot Structures for the following
molecules:
 1) PCl3
 2) OF2
 3) N2
 4) Br2
 5) O2
 6) SiF4
7) HCl
8) CS2
9) H2CO
10) C2H2
Polar vs Nonpolar Bonds
 If the electrons are shared equally, it is called a
nonpolar covalent bond. (This type of bond only
occurs if the electrons are shared between identical
atoms)
 If the electrons are shared unequally, it is called a polar
covalent bond.
Polar and Nonpolar Molecules
 Molecules can also be polar and nonpolar.
 Molecules are nonpolar if:
1) the bonds are nonpolar
2) the polar bonds are arranged symmetrically
 Molecules are polar if the polar bonds are arranged
asymmetrically.
Lewis Dot Diagrams
 Cl2
 Linear
 Nonpolar bonds
 Nonpolar molecule
 Chlorine
Lewis Dot Diagrams
 H2O
 Bent
 Polar bonds
 Polar molecule
 Dihydrogen monoxide
Lewis Dot Diagrams
 NH3
 Trigonal pyramidal
 Polar bonds
 Polar molecule
 Nitrogen trihydride
Lewis Dot Diagrams
 CH4
 Tetrahedral
 Polar bonds
 Nonpolar molecule
 Carbon tetrahydride
In covalent compounds, atoms become
stable by ___ their valence electrons.
5%
95%
transferring
2. sharing
1.
A ___ covalent bond is the result of an
equal share of electrons by both atoms.
11%
89%
polar
2. nonpolar
1.
A cation has a ___ charge.
100%
0%
positive
2. negative
1.
When an atom ___ electrons, it becomes
positively charged.
5%
95%
gains
2. loses
1.
In the formula CO2, the number 2 is
called a ___.
0%
0%
0%
100%
superscript
2. oxidation number
3. charge
4. subscript
1.
What is the correct name for
PCl3?
0%
0%
100%
0%
Monophosphorus trichloride
2. Phosphorus chloride
3. Phosphorus trichloride
4. Traphosphorus chloride
1.
What is the correct name for
Li2O?
11%
37%
26%
26%
Lithium oxide
2. Dilithium oxide
3. Lithium (II) oxide
4. Lithium dioxide
1.
Which is not a diatomic
molecule?
11%
22%
11%
56%
Fluorine
2. Nitrogen
3. Bromine
4. Boron
1.
Which element is a nonmetal?
11%
0%
89%
0%
Boron
2. Lithium
3. Carbon
4. Magnesium
1.
Which element has 7 valence
electrons?
0%
0%
100%
0%
Boron
2. Nitrogen
3. Fluorine
4. Manganese
1.
Noble gases are stable because
they have __ valence electrons.
0%
0%
0%
100%
2
2. 4
3. 6
4. 8
1.
The noble gases are in which
block of the periodic table?
6%
61%
22%
11%
s
2. p
3. d
4. f
1.
Electrons have what charge?
84%
16%
0%
-1
2. +1
3. 0
1.
How many valence electrons are in an
atom of oxygen?
0%
0%
100%
0%
2
2. 4
3. 6
4. 8
1.
How many shared pairs are
present?
0%
100%
0%
0%
1
2. 2
3. 3
4. 4
1.
How many electrons are not
shared?
5%
26%
0%
68%
1
2. 2
3. 3
4. 4
1.
How many single bonds are
present?
5%
63%
0%
32%
1
2. 2
3. 3
4. 4
1.
Are the bonds polar or
nonpolar?
74%
26%
Polar
2. Nonpolar
1.
What is the shape of the
molecule?
21%
63%
0%
16%
Linear
2. Bent
3. Trigonal pyramidal
4. Tetrahedral
1.
Is the molecule polar or
nonpolar?
63%
37%
Polar
2. Nonpolar
1.
10 ml of the substance has a mass of 9 g.
What is its density?
79%
5%
16%
0%
0.9 g/ml
2. 1.0 g/ml
3. 1.1 g/ml
4. 19 g/ml
1.
What is the percent oxygen in
the substance?
11%
61%
22%
6%
11%
2. 33%
3. 67%
4. 89%
1.
Double and Triple Bonds
 A double covalent bond occurs when two atoms share
two pairs (4 electrons) of electrons.
 A triple covalent bond occurs when two atoms share
three pairs (6 electrons) of electrons.
Examples of compounds
consisting of double bonds.
 CO2
 O2
 C2H4
Examples of compounds
consisting of triple bonds.
 N2
 HCN
 C2H2